Garthanos
Arcadian Knight
Yeah, IMHO the only issue with themes is they did increase complexity. Had they been introduced in the original core game they could have simply elided a few non-theme elements so that your theme could provide a bit of what class normally does (and maybe there could be an option to not have one and claw back what you'd 'lose' for it). The themes themselves are pretty good, although there are some clunkers in there the bulk of them are usable, if not mechanically good choices.
I actively liked Themes for that sense of flexibility in character design and they had the same niche as paragon path and epic destiny. I actually reacted to many of the paragon paths as why isn't this something you are already building towards in heroic why are they boom suddenly there ... with the themes in place that response is less worrisome (not actually sure why).