No. I’d never call it “liner” as that is also a specifically defined thing as @HibiscusKazeneko stated. A thin little sleeve for holding the actual disk.
Hence why I gravitated to “booklet” as the closest thing I could make sense of from the choices. This is now the common way to replace a book. And in many cases once an extra couple of sheets are glued in then it becomes a bigger book.
OK, and sometimes there are even lyrics printed all over it, but there might be a real booklet included too. … I thought, this would be a simple question with an immediate answer, but seems to be difficult too.
Off topic:
I need a relationship for a work with lyrics from another work. I have made it “based on” the first work, but how can I say that it reused its lyrics.
I have other items with two booklets. One of lyrics, the other of promo stuff. Tucked into a cardboard gatefold! Hence with me “if useful information is written on it, then it becomes a book”. A “book” can define a single one page sheet of paper up to a full multi-page novel included with the CD. (And yes, I have those too = LOLz)
It is the classic issue of trying to make things fit into a category. 
You missed last year’s debate trying to define Male\Female\Other. The more you try and make boxes to fit things in to, the more boxes you then need when you realise how much doesn’t fit. 
Slipcases and Boxes are also a headache. And then there is the boxset of Jewel Cases when you can end up with loads of “Fronts” and “Backs”.
The key is to make use of the notes. Label things clearly as you go. Use a bit of common sense. And be prepared to return to everything one day when new categories appear.
Only the outer most package should be Front and Back.
This is why Boxset needs something new. Often a boxset can be literally that. A simple box. And inside the box is just six standard jewel cases. Six Releases that can be found elsewhere in the MB database with their individual Fronts, Backs, Mediums and Booklets. And here we have a new cardboard wrapper around them to make then a new set.
Puzzling.
Here is a simple example I added myself. This is a simple box, with six CD jewel cases inside, and the CDs are also available separately.
Here is a much more complex example. Only 230 images attached by another editor…
That one is a box set of boxed releases also listed as separate boxes! I think the labelling makes sense of the chaos!
Yeah, this is the pattern I have been taught. Label the Front of the separate Releases. And the Back of those Releases.
In my early days I made a few mistakes thinking the booklets had backs too, but they don’t. Just page numbers to add to the Comment field.
But you are only doing small boxes…
Only the 238 images uploaded by tigerman325 there… epic work…
Every Release is in a little Gatefold sleeve, with one or two CDs in there, and a little booklet. For each release. I have a Chinese knock-off of this and was sooooo glad to see that tigerman325 had already done the heavy lifting. I could then just add the oddities from my box.
I am rather glad the Ozrics box I did last week didn’t have any booklets in it.
I’m glad to posses no such releases! Really impressive!
@HibiscusKazeneko: would you think that’s an attached liner. It’s glued to the backside of the back cover (it’s a kind of book)
Yeah, I’d think so. I’ve seen packaging like that a few times. You could select both “booklet” and “liner” for that one; it looks like the back page of a booklet on the opposite side
I’ve done so!
In fact this page is part of the hard cover and the last page of the actual booklet is glued to the back of it. I have set it to “booklet” nevertheless. (the inner part is a real booklet - see page 18&19)
I guess an official decision must have been reached on the cardboard sleeve replicas that house the CD’s included in a boxset being liner’s. Editors are now changing the front/back designations to liner. I do not agree or disagree on this, boxsets have always been a problem with Musicbrainz. Is the next step to edit all the front/back/spine settings of jewel cases that are in a box set to liner?
But that doesn’t make sense. Was there a discussion on this? Do you have an example where it is being changed?
I accidentally came across the edits which were done today, I chose not to look closer and added this post in hopes that it world not continue until a consensus was reached on this issue and how edits would be applied to existing releases.
I would not appreciate this, but could you give an example?
Front, back and spine should be reserved for outer most surface of package, what is visible when all is closed.
So, spine can be ok if it is actually visible from the outside.
But front and back are not ok for inner packages (except if outer package is clear/transparent), there is only 1 front and 1 back.
Liner is not good either for inner jewel cases.
It is good if it can match the definition (see below), like for those so called ORIGINAL ALBUM SERIES, where each CD is in an actual liner sleeve (cardboard in this case).
A liner is a protective sleeve surrounding a medium (usually a vinyl record, but sometimes a CD), often printed with notes or images.
If it was not inside the box it would be a Cardboard/Paper Sleeve.
Lets look at what is in different box sets
The Turtles The Complete Original Album Collection
6 cardboard gatefold mini replicas each with front/back/spine and inside notes.
Outside’s set to front/back/spine with a description and Inside’s set to liner with a description.
Joni Mitchell - The Studio Albums: 1968-1979
10 cardboard gatefold mini replicas each with front/back/spine and inside notes.
Each set to “other” with a description.
Frankie Valli and The Four Seasons - The Classic Albums Box (has 2 types enclosures)
16 Cardboard/Paper Sleeve mini replicas, each set to front or back, with the description set to name of album.
2 cardboard gatefold mini replicas each with front or back, inside set to other , with the description set to name of album.
Now clearly there is no consistency in these examples and all these were entered before we had “box” for a package, and yes they need editing, but not before a consensus is reached on how to handle them.
There are boxsets with jewel case, fatbox, gatefold, Cardboard/Paper Sleeve, keep case, and there will be boxsets with digipak’s. Just assume anything will be in a boxset and there may be different package types whiten the box, not just one type.
The contents of a boxset need to handled in a consistent manner. I don’t think calling a Cardboard/Paper Sleeve a liner and then calling the gatefold in the same box something else is showing consistent handling of the contents.
There shouldn’t be editing done until there has been more discussion on this.
For the record I am opposed to calling a mini replica package a liner just because it is housed in a box with other mini replica’s.
@reosarevok, I think something should be said in the documentation for this case, because we should not use Front / Back either as those are invisible from the outside…
But what to do… 
?
Allow Front and Back on things that are not visible?
The problem for me is that the real and visible Front and real Back are not found easily, or at all.
We are dealing with the art work of a package that is in a package, which I call a “sub-package”. It appears the art “label type” was designed for a singular package and not to describe or label a sub-package. Since front/back/spine describe the outer package they probably should not be used to describe the sub-packages, also the use of front is very special and positional since the first front is is used for display.
I think “other” is the correct choice (for now) with the comment field being used to accurately describe the sub-package, in a way it could be parsed. With so many different variations of box contents that could get tricky. Something like medium position, package type, art type, sort of like the following but with many more permutations.
CD1:Sleeve:front
CD1:Sleeve:back
CD2:Gatefold:front/back/spine
CD2:Gatefold:inside
CD3:jewel:front
CD3:jewel:back/spine
I agree. Currently Cover Art / Types Guidelines say:
“The album cover, this is the front of the packaging of an audio recording (…).”
This is true for “inner covers” too, especially if it’s only some covers of previous releases packed together in a box. Most users struggle with this definition.
I have added only one box set so far. In this case 4 of 5 inner CD covers would meet the definition of “liner” then. (1-piece cardboard cover)
Would be good solution, but there should be a comprehensive explanation for this rule and I wonder, if many users will follow.
I have to disagree, why should there only be a single front image if there are e.g. multiple jewel cases (with front covers for each) inside a cardboard box? For me it’s absolutely fine to label all their covers as front, because that’s what they are.
I always choose the best matching type and do not obey to some rather strict definitions that are not even stated in the guidelines. And AIUI the definition of other gives me right:
Other
Anything which doesn’t fit in the types defined above.
These “inner front images” definitely fit the type front best and therefore should not be labeled as other. Else almost every image of a huge box set would have just the type other - and this would not help anyone.
But I agree that the current flat system of artwork types is not suitable for non-trivial packages, same as the packaging types themselves. As long as we have no hierarchical grouping for these, it’s best to order the images of type front by packaging hierarchy. This makes sure, the first front image that is displayed will always be the front cover of the outermost packaging. Hence there is no harm to have multiple images labeled front.