Going for a wooden look. Cant seem to keep "good" depth and shading on the upper part of the "T"


http://img10.imageshack.us/img10/4958/twillilogo.png

I havent done the left part of the "T" yet where the branches stick out, so ignore the plainness there, Im asking for help on the large spot, with less than alright shading/depth.

Umm, any help or C+C would be more than welcome. Im trying to get this looking good.