GNU Image Manipulation Program - That is, GIMP. GIMP is an art program not disimilar to Photoshop that can be used for a great variety of art and photo editing.
Below are two Gimped images (100% copyright, yes) that I have created. The first is a comission I did for one of my workmates; a Corgi puppy called Ruby. There are quite a few steps to creating images like these, but both came from simple sketches and were shaded using dodge/burn tools. Colour added (30% opacity), background of faded phot added using the eraser on incremental. For the second image, the sketch was in dark texta, creating slightly better lines for colouring. I shall, in future, be adding some Gimp tutorials on how to do these kinds of images (and photo blending using the eraser, an absolutely brilliant skill.)