Many people believe that your genetics determine how high your biceps will peak. This is true but it does not mean that you can't do something about it and try to win nature on your side.
There are two types of biceps depending on muscle belly length - short and long:
Long muscle belly
The length of your biceps will usually determine how high your biceps will peak. People with long muscle bellies have smaller peaks while people with longer tendons and shorter muscles tend to have greater peaks and usually get them easier. At the same time the trainees with long bellies have that powerful full arm development look and have easier time building general mass.
Those are the genetic factors - you can't change them. It doesn't matter what exercises you do. You will never change the length of your muscles and tendons. You have a better chance proving that Pamela Anderson is a virgin than achieving the above goal.
Ok. Let's now talk about the stuff you can do.
Larry Scott, the man who knows more about arm training than anybody else, recommends working the brachialis - a small muscle between your biceps and triceps.
Short muscle belly
Developed brachialis will push your biceps up and make it peak higher.
In case you wonder why you can't see your brachialis - it's a small muscle and you need very low body-fat levels in order to make it visible.
The spider curls are Larry Scott's favorite exercise for developing the peak and the brachialis.
Watch the video below for complete demonstration of the exercise done by The Legend himself:
As you can see there is a way to improve your biceps peak through training despite what everybody says. Larry Scott, the man with the greatest arms ever, has already proven that this method works.
The following video is an excerpt from one of his seminars - pay special attention to how his biceps changed after adding the spider curl and keep in mind that Larry Scott has long muscle bellies which make the development of a good peak harder.
Of course don't expect to get the peak of genetic gifted individuals such as Albert Beckles who has used his short muscle to his advantage as much as possible. At the same time keep in mind that results come to people training hard in the right direction and good genetics without hard work are wasted talent.