It's great to be able to change *colors* of your themes, but many times the worst thing about your themes is the amount of padding/line-height you've chosen.  Please allow Theme Builder to customize that, OR at the very least give us an option like GMail used to do (don't know if they still do) where you can have "cozy", "comfortable", "small", "huge", etc.

A great example of how odd too much padding can be is right here on this page.  When typing this new suggestion, the drop-down box to choose a "category" has wasted height.