I think you should narrow it down so you can have a focus instead of an array. Music sounds good though.. the current song you're listening to, what does it look like? could be animal, human, inanimate object like a unique design of a lamp which symbolizes the song for example. or if it talks about a room.. design the room which the song inspires. ya know?
food can be another theme separate .. probably not imagination wise, but drawing food in general. I have yet to see people draw still life. like your dinner for that night.. if its delicious and savory .. why not draw it?
Next themes would be of the 5 Senses? I like K0n's ideas :3 but i like it broken up a bit so it touches on different art styles and gives a chance for others to step in since maybe not everybody can draw imagination but technical or try something new.
(¸.·´ (¸.·`¤.Tea.. ¤