A unit plan allows art teachers to connect many ideas into one single theme. I think they can really allow students and teachers to explore a single theme. Unit planning provides you with a sense of direction and organization that again helps you and the class to achieve significant academic gains.
For me, I plan to have my unit being based off the theme of narratives in art. Students today are constantly being surrounded by narratives. Moves, TV, Advertisements, photographs. They may be unaware of it but they are creating their own narratives when they post photos using their phones or cameras, and post you tube videos!