After you've included regular straight rows within the program, you may also want to consider adding reverse-grip rows as well. These are going to place a slightly greater stress on the biceps muscles as opposed to straight rows, so they will be a better exercise for strictly targeting the biceps.
Depending on what muscle group you think of contracting as you bring the weights up to the body (the biceps or the back), that too will impact the nature of the muscle stimulus.