I think it looks off because Tweety didn't render in the eyes or the mouth polygons. I think the base texturing looks really detailed. Just out of curiosity will the spec, occlusion and stuff help with the dirt on his face? Right now it almost looks a little like cammo paint smeared on.
Regardless I really like your texturing, especially the shirt. Gives me inspiration to work towards!
~To create a new world through the imagination