I did Halloween and Christmas (2011 was my first year.)
If I had smart strings, I'd be tempted to do other holidays. My g/f suggested Easter and I can only think of 2 Easter songs (Peter Cottontail and Easter Parade) so I doubt that would happen. Valentine's would be relatively easy (love songs and red/white lights). St. Patrick's Day has potential. Like Chris, if I were to do another holiday I would consider 4th of July. So much music to choose from and lots of decorating potential. (Mega flag, fireworks, etc.) Granted, I doubt you celebrate that in Edmonton, but I think you get the jist.
Your only limitation is you imagination, time and budget!
Steve