I'd like to suggest to add the ability to tag (?) screenshots or otherwise constrain them to a given platform. For example Krita, the drawing application, may look different in a plasma environment than in a gnome environment than in a solus environment. To give a more native/integrated feel the authors may choose to offer platform dependent screenshots.

This would incidentally also allow appstream data to feed into the windows and apple stores, which arguably deserve their own set of native screenshots ;)