Icons for iPad are almost twice smaller than iPhone 4 icons. Icons for apps/games from appstore have 72x72 pixel size and system/cydia icons have 74x75 pixel size.
If you want request some icon for app/game from appstore, look first at the Black'UPS web site. There you find out if your requested icon isn't already made. After downloading 144x144 pixel icon you have to decrease the icon size to 72x72 pixel.
If you want the icons for cydia app, you have to open System&Cydia.psd tamplate (download coming soon) and make this icon by own.