Place a sheet of tracing paper over the image, and then use a pencil or pen to indent the image. You won't be actually drawing on the image, but rather indenting the paper so that your colored pencil or coloring medium will leave ghostly white outlines in the spots you indented. This could be as simple as adding details to flower imagery or adding zentangle_like patterns within your coloring book page. It makes for a magical effect as you color.
If you finish coloring and find yourself being critical of the end result, maybe a few tutorials on color control and shading are all you need! Or, if you find yourself getting bored with the same old colored pencils or markers you always color with, a different set of materials might be all you need.