your flesh looks terrible on both the riders and the lizard. No detail on gas cans (the most basic technique of drybrushing would have helped a lot). The riders are waaay too dirty (did you just pour wash on them?) Overall the painting is very juvenile.
Not bad at all. Nice complementery colors, and the skin of the terrasaur looks nicely done. I'd have painted the horns and claws a bit more brighter, and the houda could have used another highlight, IMO. The guys at the top look fine, although flesh wash looks a bit too stark on the arm, and the skin tone don't match that of the face.