Very minor, but this button is illegible on the search page. There's also some strange hover colour for the + and - on that same page which isn't consistent with the rest of the forums colours.
Looks good. I'll also point out that the empty grey boxes actually have icons in them, you're just unable to see them as the background colour is the same as the icons colour as shown here (I changed the icon colour client side just to show this, you can't actually see it by hovering over it or anything):