The 4.2.1 Themes for 8700 are
- AT&T
- BB Dimension Icon
- BB Dimension Today
- BB Dimension Zen
- Bell
- 02 Icon
- Vodafone Today
The 4.1 OTA download of smoothie also works.
That's all I've gotten so far. Since Smoothie works, I would theorize that anything from theme builder would as well. None of the other vendor or any OTA themes from mobile.blackberry.com will work.