Babs: some pre-teens can paint well believe it or not, so don't go steortyping the quality. As a pre-teen, I was better than half my local stores adults.
the red spikes seem to be overdoing it a bit. The thing that stood out to me is the green, though. I think it ooks rather silly (like plastic) on the rings, it looks positively spot-on for the cables and tubing, with the eyes and targeting lens on the barrel the same color. It really sets off the piece. If it were me, I'd do something else with the skull on the front (hang it on a chain perhaps) and redo the spikes in a more neutral color, losing the helmet spike and the front/back spikes altogether.
Did you use a beastman face for the guardsman? that's a pretty neat conversion. So yeah, some criticism. But your painting is pretty darn good, you show a lot of promise. Next step, let's get you highlighting!