It depends if you want traditional boys room - with blues, reds, browns, and dark greens, or if you'd like a more modern boys room with chocolate browns, oranges, yellows, greens, etc..

Decide if you want a themed room: sports, transportation, boating, race cars, etc.. or if you would like more abstract theme with colors instead. Then I would look through magazines, internet sites and Houzz (of course) at other boys bedrooms to inspire you.

Here's some ideas:

http://www.houzz.com/ideabooks/query/boys%20bedroom