If I find creativity just isn't happening for me, I go to my local thrift shop and purchase a painting or two. I set these up where I can see them and then just look at them. Sometimes inspiration comes to me immediately and other times it alludes me for days. It just takes time and practice to get your mind out of the "patterned" mindset. Sit down with a painting and see if there is something missing; such as a landscape painting of a farm. Should there be animals? Is there a windmill? Why aren't there ducks in the pond?
Once you see what isn't there, but should be, think about how to put that item in there. You can paint items in the way David Irvine does.
(If you find you want to give this a try, stop by the Creative Bug Blog and see a step-by-step tutorial! It looks easy because it is!)