Here's an idea for later:
Sometimes you need to create a map on the fly. In the middle of the game, and you actually don't want it to take longer than a minute. Finding art with roll20 is fast, but when you have to slap together a map with some enemies it all adds up. 20 seconds for that tile, 20 seconds for the other one, 20 seconds for the orc...
That's what the "0-second" library would be for. It would be a sub-tab on the art library tab that has a very limited, fixed amount of tiles and tokens available. It'd be limited and fixed, so it is really fast to find something, and so generic that you could use it for anything (ok, you'll have to tell your players what is what, but that's the same on a real table).
Contents (a couple of sections):
Section "Tiles": Grass, Shrubbery, Dirt, Stone, Wood, Street, Water, Sand; Wall, Stairs, Door, Generic Furniture, Tree
Section "Fantasy": Warrior, Archer, Wizard, Crossbowman, Dwarf, Elf, Soldier, Bandit, unarmed peasant... (I'd say 12 or 16 max), and a Horse
Section "Monsters": Orc, Skeleton, Zombie, Dragon... (I'd say 12 or 16 max)
Section "Modern": Man, Woman, Cowboy, Gunman, Sniper, Robot, ... (again, 12 to 16), and a Car
That'd be it. 4 tabs with 16 tokens. No more, no options, no dupes. Slap together an encounter with these in a minute. Won't look nice or original, but it will be fast.