It's possible to select from a list of 21 predefined characters, or import those you've made yourself from The Sims game. However, it really only serves as a secondary aspect of the simulation, and doesn't directly influence gameplay mechanics. The idea being to establish up to 5 Sims per city, giving them a place to interact and see how they feel and respond to their surroundings from speech balloons. I'm sure many of you will have heard of MySim Mode in SC4.
In our 1st official CoriBoom™ release to the STEX, and I have humbly created a mod collectively designed for everyone here at Simtropolis. Simtropolis Members immortalized in SimCity 4!