I guess he was wondering why, when you select your car/livery, there are no preview pictures of the mod cars one just added. I am actually experiencing the same problem.
modders being folk who rightfully and proudly show off their work, if it could be easily inserted as a preview in the game, i figure they'd have done it by now. i always only run one modded skin and cars stay on the skin you used last, so after you found it once, you automatically find it again.