This question already has an answer here:
Can "Identification questions containing only an image are off-topic here" be explicitly added to the guidelines for identify-this-x questions?
It would seem by convention that identify-this-x questions asking for help identifying the source of an image are not allowed on this Stack Exchange. This isn't clearly expressed in the guidelines for such questions, which, while they ask for as much information as possible (listing many different pieces of possible data) do not mention images, either positively or negatively.
As images convey a significant amount of information and are not explicitly disallowed, it is not clear to users unfamiliar with this SE that those questions are not appropriate.