Let’s see what the outcome from URL/contact fields in snap metadata is for contact. I am weary of just throwing in new fields.
For screenshot I think it would be nice to see either
meta/gui/
screenshot_1.png
screenshot_2.png
...
screenshot_N.png
Are there upper limits to the amount of screenshots, if not, should there be? (my guess is yes)
From a snapcraft PoV we will treat this as we do for hooks, either put them in snap/gui/... or make sure they end up through some build process into prime/snap/gui (some cases might have this handled automatically e.g.; declared appstream entries).