I think it's more about personal opinion. For me, I don't like a car with a lot of decals. Specially on the body. On the glass is one thing. I prefer black or a dark color that isn't too noticeable. If you have components or special mods in your car that you wish to advertise or promote and give it that race car look, that's up to you. Nobody will knock you for it. If you like it. Do it!
If your asking me about where to place the street glow decals? I would say side glass. Click Here!