Zelda Classic tiles are sheets of random tiles that can be grabbed into your quest. They can feature a variety of things, such as overworld objects, dungeon items, sprites, or other things. They're a great way to add a unique feel to your quest, regardless of what tileset you are building with. Keep in mind that most loose tile sheets will have to be recolored after you rip them, but some are are saved in a pallete that matches a certain tileset.