Woop! Another contest, actually have time to enter this one too.
Here's my initial concept, will probably stick to diffuse/glow/alpha and keep it truly mobile spec

Grotesque, me likey! Maybe lose the stitched in look to the other arm though? If he's a mutant, surely he could have just been born with that other arm...

The 3rd arm is too short - try a tentacle?

Dude needs a tennis ball launcher arm cannon or something along those lines!

Trying to make it look more mutanty, quick liquify/paint over:

Seems like if you were modifying someone to make them beter at tennis you'd want to give them a long er reach, not reduce the length of their arms. How about stitching on an extra arm joint so that he's got two elbows on each arm.

I like that idea, and it makes sense too! i'l do some more thumbs based around this design and hopefully have something more tennis-useful:p

Had a rethink of design with my mutant, did a really rough sketch which i won't bother to show, but heres the start on the body mesh, 1.2k tris atm with a hell of alot of optimisation i can still do to it (infact i havnt really optimised it much at all yet):



And here's a paint over to show where im going with the model:

Not sure if i'm going to be sculpting or hand painting this one, so i've done a quick test sculpt to see what things may end up looking like if i went for the normal maps route...

Almost done with the base mesh, still 500 triangles to spare, probably just going to be spent on smoother silhouette:

started on the high poly, and did a little test bake for fun



Edit:
Update again

Hey gilesruscoe! This looks like Andre Agassi´s crystal meth years...:P

I liked the idea in the second concept (the grey one) that the head is kind of embedded in the shoulder parts. I mean the shoulder and the head are more or less at the same height.
I was thinking, may be the character does not need two strong arms with the same strength. may be you could exaggerate a little bit more with one of the arms. Like the arm he uses most. What do you think?

Another update on the lowpoly, just messing with bakes and some texture ideas, HP still not finished.