I'm not sure if this has been suggested, but since there are so many themed pets I thought it'd be interesting to have a bestiary where you could see how many of them you (or other users) have collected out of all the ones that exist. Maybe after you fill certain amounts of it, you could receive a title or some kind of reward?

I noticed that Sylestia doesn't have any kind of collection page that can be filled and displayed, so it could be a fun feature that would also help people keep track of which themed pets they don't yet have and want to obtain ^v^

This is something that we plan on adding, along with a few other types of codex/collection features, with the relaunch. =)