This is an inconsistency that I'm seeing pop up fairly often. We get a lot of questions dealing with "Who is this character?" with a piece of artwork supplied, with the question having a fairly unambiguous answer. Sometimes the artwork is custom or fan-made, and sometimes the artwork is official.
Here is the latest one that ran across the HNQ, currently up-voted and answered sufficiently.
Here is another one which was closed as off-topic, and I got a very firm stance that it was off-topic from one high-ranking user and was told on no uncertain terms that other questions of the same ilk were mistakenly left open and should have been closed. The comments from that discussion are in the question.
The game-identification tag gives several straightforward examples of up-voted questions of the same type (Identification of a character in fan-made artwork, Official artwork in a fan-made environment, Fan-modified game asset).
The way I see it, these fall under the help topic's criteria of "Plot and characters in games." 2B is a character from a game, as is Yennefer. But, as brought up in the off-topic question, this could be interpreted as assets from a game only, not including artwork. The artwork on the cover is not from a game, it's from a book. Likewise, the artwork on this desktop background is from a fan, not a game.
If these questions are allowed, the On-Topic page should be modified to make this clearer and the non-closed questions I linked should be explicitly labeled off-topic to prevent additional confusion. If they are allowed, then the off-topic example provided should be re-opened and possibly the On-Topic page should be made more explicit. If there's some sort of line between the examples, that should probably be codified somewhere.