Zack,
Those are off season photos. I did that shoot about four weeks ago, before I began dieting down for the Jr. USA's. The very first place to lean out on me is the shoulder and bicep region, so some of the fullness and size disappears as I get closer to competition time unless I'm fully flexed.
This past off season, I kept my diet very consistent and regular. I didn't allow my body to get out of hand, and I lifted moderately heavy to heavy in the gym...legs and upper body. I think in the past few years, I've been concerned about my biceps overpowering my shoulders, so I didn't focus as much on them. If I were going to skip a body part, arms or chest were the choices.
I do three exercises for biceps and three for triceps (right now, I'm doing a tri-set of exercises for triceps). I stick with moderate to moderately heavy weight and do about 10 to 18 reps per set, three sets per exercise. The reps are done slowly...at about a 1-2-3 count, and I squeeze the peak of the bicep at the top of the exercise on each rep until it hurts.
I'm still concerned with my arms overpowering my shoulders on the figure stage. It seems that arms are not an important body part for the figure competition, whereas shoulders tend to dominate the show. So, my mindset switches back and forth between wanting desperately to lift heavy with curls and wanting to keep my biceps in check.