I once wrote an article (in german) that there might have been even more than 7 races in an unknown past of Rivellon.
Take a look at how many houses stand there in Aleroth, and then assume 1 house for every race ...
In the council of Seven Races intro, the main character objects, reeling off a number of other races who are native to Rivellon who are not part of the Seven, IIRC...
