I know absolutely that you have other priorities right now after such a conversion/upgrade, but we really need alternate themes and/or ways to change the colors. (For now, I am using a FF extension "Color That Site!" to adjust the colors, it's hurting my eyes otherwise).
I have seen on the actual Xenforo forum that Xenforo (no suprise) is super-complex, and the default theme looks actually "decent", so no question there is huge room for tweaks.
Also: Left navigation/category bar...PLEASE....and all the information on the right I think is relatively (ok, correction: absolutely) worthless. "5 new posts" in such a big forum is silly, the information about online members, staff online etc. is not needed.
The blinking green dot when a user is online is more annoying than actually helpful/useful.
Those are actually all MINOR tweaks since with only a little tweaking of the colors in the mentioned extension it's actually...useable. Now add the left navi button and it would be great