Trying to find a site where you can create a virtual car customization and get a wide variety of vehicles to select from is going to be tough right now. At this time much of what you will find has to do with custom tire and wheel combinations and auto body kits for a custom look on your car. There are some sites that offer some auto accessories and parts specifically for building a personalized custom vehicle but they don’t give a virtual image of the changes you make.
You can also find plenty of great car tuning content about making car modifications in order to improve the performance and handling of your vehicle so to mirror your driving style but nothing more. We also did a search for any site using this capability to showcase custom car interiors but no luck there either. Our suggestion is that you keep checking for a site like this, I’m sure someone will fill this niche soon enough and if not maybe RaceFan365 will take it up.