I like to make the distinction between digital photographs and digital images. To me a photograph has minimal post production, the closer the image is to the camera the closer it is to being a photograph. When you start changing the the elements within the composition then you start creating a digital image.
There are some post production techniques that are analogous to the work done by chemical / film photographers and I reckon those would be acceptable to use to keep a composition a photograph. So things like resizing and changing levels etc would be allowable.
I decided I wanted to do more than just levels with my favorite image from my photo shoot with Tonya Z. I wanted to do something a little artistic, and maybe a little meta. I used Photoshop to alter a reflection and create a painting inside my digital image.