[[File:DoesNotExist.jpg|some text]] renders as the red text "some text", instead of the red text "DoesNotExist.jpg". I think it should be the latter. Parsoid renders it as the latter, as well. If this is a WONTFIX, we should re-examine the Parsoid behavior, because that's an inconsistency between the two parsers.
The non-image redlink [[Does not exist|some text]] also renders as "some text" instead of "Does not exist". So at least in that sense, this behavior is consistent. Though on the other hand, nothing special happens for redlinked categories (they get added to the page exactly the same as bluelinked categories), so there could be an argument for consistency in that direction too I guess.