I thought it'd be useful to compile a list of themes that work or don't work... given how many of them there are and how broken some of them are.
1. Forum or Board Default - Yes
2. SMF Default Theme - Core - Yes
3. Classic YaBB SE Theme - Yes
4. Babylon Theme - Yes
5. Loger - No
6. So1o - No
7. MegaPolis - No
8. reload - No
9. SMF:BW - No
10. Outline - No
11. Overview - No
12. Brkdmrcn_v4 - No
13. extreme10 - Yes (Original bcfurries theme)
14. orange-lt119v1 - Yes
15. Urban - Somewhat. (Has dummy menu items, and the help/search/profile/mymessages/calendar/members are in the second dropdown menu without any text in it.
16. DS-Natural - Yes (Christmas bcfurries theme)
17. Amber - Somewhat. (Looks like it's got some minor graphical glitches.)
18. Nurumuz - Yes.
19. Nly-Grey - Yes.
20. blue23 - Yes.
21. Pixel Perfect v1 - No.
22. dark4 - Yes.
23. Analysis - No (The TOP one is broken.)
24. Analysis - Yes.
25. As Theme - Yes.
26. BlueMax - Yes.
27. corp-lt119v1 - Yes.
28. SMF-Orangie - Yes.
29. Several - Yes.
30. Novus - Yes.
31. Indigo - Yes.
32. Swan - Somewhat. (Navigation bar is broken.)
33. Swan - Yes (but, this one should be removed as it violates the usage rights of the 2010 logos, and a former member would object to it being used as it's his work and stuff...)
Phew. I think that's it.