This is much about personal taste, but a bright-white background is not everyone's first choice. So maybe it would be possible to add some options to enable the user to change the colours of the different windows, panels etc.?
I would also be fine with a pointer to a .xml file to edit it myself. Just need to get rid of that white ;)

But before you go about responding to the color request with your usual deft efficiency, please let me request...
Please leave the white as a first choice. I use Metabolt often in my RL workplace, and it looks much like any other generic directory or dialog window. The last thing I want is for Metabolt's IM window to start looking like the purple Yahoo chat window.or something else to catch the eye.