Yes, some sort of avatar management would be great
There's currently 600+ avatars, which means 100+ pages and no way to sort/search, except for looking manually.
Also, I see "!" every time I get a new avatar, so if I wanna get rid of it, I gotta click on "next page" 50-80-100 times. And then I get another avatar... Pretty annoying.
Small updates:
A button to remove the "!" for new items and/or avatars. Something like the "mark all as read" in e-mail.
Would be nice to get avatars sorted by Owned/Not Owned/All
Bigger updates:
Sorting by Girl Name, Related Event and Release Date would also be nice.
After that you can think about Integrating avatars with the Harem Page - each Girl Page in the Harem to have a link towards a Page (or search result) with only that girl's avatars.