Hi Liz,
No matter how good a photograph is in its raw form, it's only when you start to take control of contrast that you really get to see its full potential. As a young photographer I often spent many hours in the darkroom trying to get the contrast just right.
Nowadays learning to manage contrast is a lot easier; you can open any photograph on your computer screen and use the contrast tools to quickly and easily adjust photographs.
Adjusting contrast is about all that you need to do to improve this image – otherwise the concept and design is great.
The simplest way to add some contrast to this image would be to use the Curves adjustment. When you open this panel just bring the shadow end of the adjustment across a slight touch and then pull the highlight adjustment across so that it is the edge of the histogram. Then if you want, you can push the middle of the curves line upwards a bit just to brighten the midtones.
Good effort.
Image Doctor's edited version
