Personally, I think guys who don't lock out on triceps movements are robbing themselves. Just feel your tri as you flex it through a full range of motion and you'll know what I am talking about.
Also, man, don't make yourself crazy looking at pics of pro bodybuilders. I am assuming that is you in your avatar and your triceps look fine, don't stress over it, your tris are in proportion to the rest of you. Look at the pic of that guy. Do you have his chest, biceps, lats, shoulders, back? No, so don't expect his triceps. Also, that dude's tris looked clean, but if you look at a lot of pro's you'll be like "How did he develop that muscle" , and he probably shot some Synthol in it. Anyway, my point is you're making progress and you look fine, lock out your triceps movements and see the difference that makes.