So it was like the EA Sports Series from like 2001-08ish?Well, kind of. You cannot use Photoshop to create a unique base with sponsors and numbers of your choosing. Instead pre made templates are available and then you can choose three colors, which will automatically be applied to a template of your choosing. You can apply sponsors available through iRacing, including the make of the car, such as Pontiac and Chevy, your Club logo from your region, and other assorted sponsors. The Jetta has an extremely wide variety of sponsors available. Your number is not put on the base, but instead it is applied when you join a server or race, depending on your skill level compared to other drivers ascending from 1.
The system allows for anyone to quickly paint there cars, helmets, and suit without needing a hassle of arranging files. It has been hinted at by Brian Simpson that custom templates may be in the pipeline at iRacing, but it is not available at the moment.