Carrara has some nice plugins to do cel style images and they have some very good easy to follow video tutorials on how to model a city from the ground up.
The old 1st edition of Figures, Characters and Avatars: The Official Guide to Using DAZ Studio to Create Beautiful Art , by Les Pardew comes with a disk that has a copy of Hexagon a 3D modeling program, Carrara 6 Pro, The Victoria 4 Pro Bundle, the Michael 4 Pro Bundle, Aiko 4 Starter, Hiro 4 Starter and some other content.
Because the book has all this stuff on the disk it comes with it is a major recommendation to beginners, despite that the book covers an older build of DAZ Studio.
http://www.amazon.com/Figures-Characters-Avatars-Official-Beautiful/dp/1598638165
You need to contact DAZ to get the Hexagon serial and Carrara 6 serial. The Hexagon build on the disk uses a different serial from the current build.
So keep a copy of your purchase receipt for the book as you may be asked to send it.
You can also do animations in DAZ, Carrara, etc. and easily make a sprite sheet out of the animation too.
I can dig out the the tutorial links if any one is interested in how to do this for sprite sheets.
Also, you could make some 3D renders of animated stuff to add for your parallax map to be used as events on the map and you are going to want to make some custom tiles for some things on your map.
The traffic lights in Dragoness Edge 2820 uses a custom tile set to add in some features onto the parallax maps for things like the traffic lights so you move under them in the game and not over them.