Haha, he's jacked. Take my word for it, lol.
I see plenty of shape in your back if you ask me...wide, solid. Only thing you could do to get more shape would be to cut more...lower your bf% a little like BBC said. Doesn't look like you have much (if any) to lower though, haha.
If you've ever run anything illegal, you won't get much definition...you'll be huge, but won't get cut until you're off cycle, due to water bloat. (I'm not saying you are doing anything illegal, and I'm not reccommending it...I'm just stating fact here.)
I stick with Whey Protein, and I have taken Creatine before. Creatine will give you a fuller look (not much, but a little) because it floods your muscles with more water...it also helps recovery time because of that. It will also make your muscles harder. It's not for some people though...you'd have to try it and see if it's for you or not.
By your looks though, you already knew all this...