I get inspiration from seeing other people work, or from seeing new things, places, and ideas. Sometimes looking at pictures other people draw will inspire you to think of something else, and you get that "Holy crap, this idea is going to look epic on paper" kind of feeling. Looking at photos and reading can also give you inspiration.
Since I also work on digital art, sometimes I'd browse speed paints on YouTube and see new techniques that I'd like to try. This gets me working as well.
I once went through an art block that lasted for a year and seven months. Pretty darn horrible. It's easy to get stuck like that without inspiration.