Have you ever seen a map with all the tiles in it? I haven't, but if you succeed in making one, I'd love to know how you achieved it.
You can increase the number of ground textures up to 16 with World Editor Unlimited or JASSNewGenPack, but you can't get past that amount. For a while, it was thought that changing the tiles through triggers would allow you to place any texture on the map. The function was inclusively implemented in one or two RP maps. However, it was later found out that placing a ground texture which the map doesn't use will only make it place an existing tile, which means you are still limited to 16.