Clockwork allows flashing of anything, roms, kernals, themes, packs of apks... there really isn't a limit.
The issue is what is locked on the phone and what dev support we get. For instance, a friends vibrant uses clockwork to flash roms, kernals and modems, and there are many of each. For my d2, I don't think I've seen custom kernals, just roms.
Sent from my LGB v0.9 Gingercomb Juiced DROID2