Incorporate all of the following into your workouts, eat plenty, and make sure your get adequate rest and I see no reason why you cant have a BEASTLY back.
Wide Grip Pull Ups, Close Grip Pull ups, Hammer Grip Chins, Weighted Dead Hangs (Hands as wide as possible), Bent over row, Dumb Bell Row, Dead Lifts, RDLs, Rack Pulls, Good Mornings
Pick 5 to 6 of these exercises to do on each back day. 2-3 of the exercises shoot for higher rep ranges(8-12) the others go HEAVY! 3-6 reps is perfect. You will need to track your progress and make sure you are still progressing each time you do an exercise. If you arent getting stronger, chances are, you wont be making any muscle gains
Some people believe in a set routine, to me its way too boring and you hit plateaus much quicker. I personally used this method to build a pretty good back and I've help many people pack on the size they wanted by doing the same thing. Hope this helps! =)