There is some concern out there that if you were to put decals or vinyl graphics on your car, truck, or whatever, it's going to ruin the paint job on your car. Well that's not necessarily true. What is true though that you Should Not Apply decals or graphic to your vehicle if you just got it painted. Generally you should wait atleast 30 days to let the paint "cure" before applying anything to it. Plus the best thing to do is to ask the bodyshop what they recommend.
The only problem you'll have(if you want to call it a problem) with decals or graphic on your car, is that when you remove them, the surface that was underneath the graphic will look much newer than the rest of the vehicle. Reason being is because that section of the vehicle does not see any of the sun's UV rays while the decal is on there, so the paint doesn't get faded. Even though your car doesn't look faded at the time, you will notice a difference once the decal is removed.
You can get around this problem by waxing your car once every 2 months. If you have graphics on your vehicle, graphics meaning fixed up like the cars in the movie Fast and the Furious, it is recommended that you wax your car using a spray or liquid wax. Using this type of wax will allow you to apply some to your graphics also and plus it's easier to clean along the edges of the graphics.