Unless you got insanely good genetics that cause your arms to grow just by lifting a pencil then no you don't need to work your biceps. Take it from someone who's been in the game for years, YOU NEED TO WORK ALL YOUR BODY PARTS TO GROW. And do NOT negelect your legs, for one thing squats will make your whole damn body grow.
Space Gray 2011 335xi E92
Old: Jet Black 2007 E90 (with xenons
and modded) 328i