Steam Punk like Goblin Chieftin

I'm looking for a price range on making a few peices of art for a D&D game im running. My players will soon encounter a multi stage boss. The chiefton has many of his limbs gone from explosive accidents. His face also has a human red neck grafted on it or swirled into it. That some redneck got morphed into a goblin. He only has a leg left and has this mechanical arm attached to his back similar to Victor from League of legends or Doc Oc from Spider-Man. After the combat starts he will run around the room attaching mechanical appendages on to his stumps. A steam punk gun arm, a large mace arm with the spike bits looking like little fire crackers, and a few leg mods. Some kind of power leg/treds or spring modification still wonder what to do for his leg honestly. Then 3rd phase would be him in a full steam punk armor suit. I would want art for all 3 stages. At the bare minimum his final form and his starting stage.

I did a quick sketch but i am not great at art.