I think, when the new Sylestia comes out, these features will make a nice addition to the site.

I'd like it if we could find collectible items in the wild and from beating bosses. These items don't really have to have a specific function (like wardrobe items, equipment, costumes), they'll just be there to collect for people who like collecting things. Maybe have certain sets of items, when you collect all of those items, you get a prize like a Title, gold, etc

In addition, I think it would be great if we could have a separate public inventory where we can show off these items and people can search for items that other people have. The public inventory could also be useful for people who are looking to sell things but would rather use COD way of trading. We would pay for extra space the same way we pay for inventory space.

Not completely related to items, but it would also be convenient at times if we could turn a specific stable to private. One purpose is for people who have messy stables and would rather not anyone see that. Its similar to having the interior of your messy home on public display and there's no way to make it private. There are various reasons people would want to have private stables, and I think we should have that option.

That being said, the pets could still be found on advanced search if its a problem for having pets in the game being hidden from other users for some reason.

For the collectibles, hopefully they could be things that aren't cash only?

I think collections are nice. People naturally like to collect (collecting pets for example lol), and small, easy to get (or a little difficult to get) items add replayability for certain aspects of the game.

I know Neopets back when I played had a Gallery section for every user to showcase their items and how many of an item they had.
I also think galleries are nice for perpetuating and showcasing item art, instead of having it for only a few seasonal uses. (I love the art for these majestic seeds, or food from Winter Bakery! I'd love to put them in its own page to enjoy the full size art)