If you want to do concept art you need to improve a lot in perspective drawing and camera positioning, then you need to start to do concept art as well. Your portfolio is ok for child book covers but it barely tells me anything about your capabilities in design.
Thanks, that's what I'm working towards at the moment. Kids books are my full time job which where my site is currently aimed. I will be dividing the two areas in future once I have enough concept work but feel the need to get the ball rolling so all comments are appreciated.