The devaronian and rebel troopers are a nice mix of parts. I like the lobot head with the helmet. <--that sounds bad, but I digress. A good wash with a lighter shade of gray would bring out a lot of their uniform details.
The biker scout pilot guy looks weird to me for some reason. Maybe it's just the pudgy body sculpt and Napoleon Dynamite moonboots, but that's hardly your fault. I think it's also weird to see that head on anything other than the biker scout body. It'll probably fetch 40 bucks on ebay, so my snooty critique won't matter much!