Can anyone help me figure out what kind of dog my Tobey is? We were told at the shelter where we found him that he is a terrier mix. He is about 3 1/2 months old and he's 15#'s. Any suggestions?

Pic #1-9/12/08
Pic #2-9/15/08
Pic #3- 9/15/08
Pic #4- 9/22/08