I like your first attempt at flash photography. It looks very natural and your WB looks good. I think an easy way to accomplish what you want is to use a black backdrop and the previously suggested hair light. If you have time you can download from iTunes the free podcasts from Lastolite called Lastolite School of Photography. It is supporting Lastolite but they show you how to accomplish indoor and outdoor portrait photography. It will help you to improve your skills to then figure what you need to accomplish your goals.