1. Lots of races. The more the merrier or more conflict, which is fun.
2. Uncommonish? I like the idea of areas with high magical power, like Mage cities. Likewise, there could be other areas that have no magic at all but have expert craftsmen or warriors. 

Also, [@Hunter of Dreams] has a good point. Most uber-powered mages tend to have apprentices or scribes to assist with them. It would make sense if a few underlings tagged along with the mages.