When searching art archives, you can search by artistic style or medium, by artist name, artwork title, or something more interpretive (weeping, longing, anger, or joy). Try combining a few strings of keywords: "anger AND blue AND watercolor" and see what your results look like. If you see a style you like, read the description of the piece and try a search for other works in the same style or theme. Take your time and be open to discoveries!
While the video below is specific to the Metropolitan Museum of Art, the strategies you see here will help in all your your searches.