I scrapped the others and decided to proceed with the 4th concept. Here's what I have so far:
#1 - I had the idea of adding 3 tail/tentacle-like things to the creature.
#2 - Thought it would be interesting to take away his arms and have him use a sort of forked-tail as his arms instead. Also gave him longer legs for sprinting.
#3 - A more refined version of the original concept where he walks on his knuckles and 4 legs.
Ok everyone, here's a more finalized draft of #2. I tried giving him a new head but it wasn't looking as good as the head from #3, sooo I had to do a head transplant. I'll make a color version later.