Breaking a larger texture into smaller slices is exactly what I did with mine. I designed it around my games resolution and when done I pasted it into 256x512 slices and stitched them back together using kgPanels
http://www.wowinterface.com/download...o.php?id=20531
Btw. I'd love feedback on my graphics. Looking to see if I need to fix anything or alter it to make it better.