yeah nice colour effects - its very well integrated with the back plate.
My constructive crit would be that despite the evil alien dudes about to open a can of whoopass (or vice versa) the lead character seems rather blaze about the whole thing in his pose... i would like to see his fists clenched, head turned, crouched down a bit - something more dynamic?
good start though and a rare attention to detail with the compositing!
There are 2 things who make the compositing not so bad : the sepia tone, and the shadow of the character.
About the shadow, i would ask a question : is it possible to lock a bone on a specific axies?
(i know it is not the good topic to post that question, please apologize me for that and my bad english...)