I just came across this idea posted on Another Shade of Grey (which they found on Better Homes & Gardens) and what a great idea it is! They purchased some architectural ceiling medallions (which appear at the base of the ceiling light fixture) and simply painted them various shades of yellow. Another thing to put in my growing "home inspiration" folder. I think this would look great on the empty wall of my entranceway ...
Ceiling medallions can be found here: Architectural Depot, on Ebay, locally in Boston at the Boston Building Materials Co-op and Restore.
I recommend finding places such as the last two listed here where you can get these architectural details used ... rather than buying new. You also might happen upon some other great things that will provide inspiration!