when I feel the need for some strict painting practice I've found that if I paint out a drawing done by somebody else I can completely concentrate on the painting part, instead of giving myself the freedom to redesign along the way, the way I would with an image of my own. it's a great challenge to try and deliver on the potential of a well rendered drawing; to realize what is indicated.
I did this the other day on a drawing done by the uber-talented Mattias Adolfsson. if you aren't familiar with his work, check out his blog HERE. specifically you can see the drawing I used HERE. he is a very prolific guy with an amazing creative array of machines, characters, narratives, etc. super inspiring. and nice enough to let me share this homage.