When choosing a theme for my sons' rooms, I try to find something that will grow with them or allow their input as they develop interests. (For example Søren's room has transitioned from weather/sky to space.) Isaac's room has a travel and transportation theme. The past couple weeks I've been creating and assembling art.
The NATO alphabet poster took many attempts before I settled on one I was happy with. I could have scanned and photoshopped a final version, but I wanted it to be all hand-done.
The art wall is still a work in progress, but I'm pretty happy with the configuration and the major art pieces for the time being.