Unfortunately, we can't change muscle shape. The only thing we can do is make a muscle bigger. Some guys have great bicep peaks while others have flat blocky arms. If a guy with good peaks grows his arms, they will be even "peakier" while the guy with blocky arms will have larger blocky arms. This being said, rep range can play a little roll in creating the best shape your body will allow. Going into the higher rep range, 12 to 14, even 16 to 20 reps, can maximize your muscle's genetic shape. Also, time makes a difference. The longer you train, the more mature your muscle gets and the better it tends to look.