An alternative to painting a digital photo is to add layers for texture and interest. This is easy to do and results in beautiful images with depth and definition. This image has two layers of texture (the same texture, just reversed for the second application). You can experiment with blending modes and opacities to find the effect that you like best, and that will suit your image.
Textures are everywhere, it's fun to photograph and collect them, plus, there's quite a few available free online. If you find the color is overwhelming the image during blending, desaturate the texture layer and you'll get the benefit of texture without the interference of color.
Below is a close up of how the textures create a painterly look with the image. You can use a layer mask and selectively brush away any unwanted sections of texture. Don't forget there is a Mask Panel in CS4 that will allow you to control the Density, Feather, and Refine features. Very clever!