help adding a tileset

Is it possible to add a tileset online? It seems as though you need the tileset image file in your client folder for it to work. It works fine offline, but when online it will only work if the image is in my client folder and the server wont send the image. Is it because the image file is too big? I noticed there is a pics1.png tileset that comes with the client…so i dont know… please help.