You could just change the button texture globally. Here - I got these out of the Cube UI (sorry, I forgot the name of the guy that put it all together :( ). Put this folder in your Interface folder (NOT your Addons folder). Pings are included so you can see what they look like, blps are what actually get loaded into the game. You can use your own textures, too, if you want to make it look different. If you don't like them, just delete the folder.