I added just one more theme and tested about 5. ROYAL is a light theme that's in various shades of white, grey, purple, and reds.
There aren't very many free themes for Xenforo 2.1.x, at the moment. The ones designed for 2.0.x don't work.
As always, if you want to buy us a Xenforo theme, just drop me a line. They range from about $5 to $100. I'm also only using about half of the features either Xenforo or the various themes have.