Sunrises and Sunsets have always seemed to me to be an ideal subject for artwork. First, they are beautiful. Second, they are colorful. Third, there's flexibility in rendering the subject, regardless of the medium. Fourth, if you don't really care for a particular sunrise/sunset, just wait a few moments and it will change...or come back tomorrow for a new one. And fifth, they have you looking in the right direction for inspiration.
Below are the three reference photos for the month of May. Try your palette at depicting one or two them and submit it to me. Then, go out and enjoy some real ones.