Thanks for the resize. I was able to edit some points I wanted to put out. Mainly on BB8 regarding your light source.
Light reflects off of the ground. You accomplished this with rey's legs, but it's missing off of BB8 which throws the whole perspective out of order to me. Your sphere looked sort of flat because the shadows were off, and thus the perspective. Rounder objects tend to be the ones that capture ground reflection(whatever it's called) the best. also BB8's head should have a cast shadow over his body, at least according to references I looked at.
Also an Idea would be to go more in depth on your cast shadows. I tried to give you an idea of what I mean, they aren't perfect though.
My final note I wanted to point out was on rey's cloth. The fold flying in the breeze, didn't really resemble that to me. The reason because it was much to flat and square, which resembles cardboard rather than cloth to me. To fix this, try making the flap thing, less consistent.
Hope this helps.