top left and middle sketches don't appeal to me at all, although the idea with the top left one is intriguing, i just don't like the execution on that attempt.
top right sketch is nice, but i don't like the eyes and nose, and if you're gonna go with the keyboard as mouth/teeth idea (an idea i always liked), i'd prefer you use a keyboard as similar to the tb303's as possible.
bottom left sketch is even nicer, except that it reminds me of uke too much, which i don't like.
bottom right sketch doesn't remind me of myself as a caricature, other than the beard perhaps.