New crazy idea: a set of VTT graphics made to be used with a virtual battlemap where the "map" is the sort of tetris-style inventory layout that old dungeon crawl video games have. There are plenty of games like this, but the one closest to my heart (or at least my memory haha) is the one from Might and Magic VII.
They'd be at some kind of standard size that slots together directly on a grid (like idk, 100x100px tiles) and you'd create your "map" out of a bunch of them, with one for each character and then like a central "shop" to keep extras.
I whipped this up at 5am so hopefully I can be forgiven for some inconsistancies!!! But this example was made for Ryuutama, so the idea was to use approximately two grid squares for each 1 item size, so a size 1 item would be two squares, a size 3 item would be six squares, and a size 5 item would be nine squares. characters start with 3+STR carrying capacity and can technically carry more than their capacity if they're willing to take penalties, so I figured you could just use a different color bg on some of them to show which were "overflow" and then adjust them as the character levels up.
In my dream world where I have All The Time to make this, I would also love to make a few different-shaped "mannequins" for that kind of paperdoll-style equipment system, with the hopes that people could use them as a base to draw on their own characters, hehe.