There are plenty of wheels. I remember when I first bought my e34 I really wanted M parallels. They look great and they are a BMW wheel. Although, don't be afraid fo going with aftermarket wheels. Check out
www.tirerack.com for wheels. You're lookign to get wheels in a 5x120 pattern with a offset between +37 and +42 all around. Try and stay unstaggered.
Good Luck