@jbarsant @dansup @PixelFed i think it's possible or even really the meta-default to have them be kept and given a cover -- the expiration is built on top of that. there's definitely room to tweak the design of the feature as well, so it's not like they have to end up exactly like instagram or snapchat.
as far as importing existing ones from instagram, that depends on whether instagram includes them in exported archives, and whether they're in a format that's easily convertible. so maybe not?