I noticed when I change banners on my Профиль page, the old ones are saved. Is there a to how many Ты can save and can I Удалить banners once they're saved?

So far I don't find any of how many banners Ты can save. And Ты can't Удалить any of banners Ты save here.

The reason Ты can't Удалить banners (or backgrounds) is probably because you've spent Золото buying them in the first place. If Ты deleted them, Ты wouldn't have what Ты spent the Золото for any more. They might make it possible to Удалить these things in exchange for returning the Золото in future.