Converting a photograph to digital?

Hi there! I have a painting I done many moons ago and have it on my computer. What I would like to do is enhance this picture to look more realistic. It is a painting of a cheetah, which doesn't look to bad as it is (even if I say so myself), but I would like it enhanced so as to see actual fur on the cat, and dry gr on the ground. Can anyone tell what software I would have to use and how to go about it. I am messing about with PS4 at the moment...am I on the right track?