At a glance, I'd say you definitely need more contrast. Try to really deepen the dark areas. Also, play around more with using warmer and colder colors to create depth and shadow.
I HIGHLY recommend Oil Painting Secrets from a Master by Linda Cateura. My oil painting teacher worshiped that book, and for good reason. It's also fairly cheap.
I really like your style, and hope you continue to post as it develops :)