Using one sprite sheet for the sprites of many objects-- and also depth of individual tiles in a tileset.

I am making a top-down RPG. Everything was going great. I made all my floors and walls in one sprite sheet, and physical objects (think furniture, trees, etc.) in another sprite sheet, and used tile set layers to paint them into the world to construct my rooms. Perfect! Tilesets made this very easy and I did not need a mess of files.. "tree1.png... tree2.png... bookcase1.png... etc.". Just a spritesheet.

Well, I realized (please correct me if I'm wrong) that the entire tileset layer must be...

Using one sprite sheet for the sprites of many objects-- and also depth of individual tiles in a tileset.