Here is Lu-Ho's tut on how to add (not replace) new tilesets: http://www.pokecommunity.com/showthread.php?t=156018
Here is a tutorial on adding tilesets in general: http://www.pokecommunity.com/showthread.php?t=186982
Like FBI said, just type in tile sets and hit search!:D
And another good tutorial, (I hope...:)): http://www.pokecommunity.com/showthread.php?t=193377
For animating tiles, this should be useful: http://www.pokecommunity.com/showthread.php?t=260619
Now I am just going to use a spoiler: