Worst place.
*ding!*
(sorry, most of you prolly won't get that...)
Anyway, on a serious note, I got Eibach stickers when I bought springs from them. I know you get AEM stickers when you buy their intakes, or at least someone I know did. I got Kicker stickers when I bought any of their stuff (6 amps, 9 subs so far... ugh... I need a new hobby). Please resist the urge, though... don't put stickers on if you don't have the parts. And even if you do, don't go overboard. If you have actual sponsors, it's all good....
It's just me, but I see tons of auto stickers as being kinda a "cheap" look as opposed to having actual sponsorships or a clean car. Then there are the custom paint jobs (see Eddie's gen4 for example) or full-length decals (my girlfriend has one of these) which I generally like, if done right...
I save the stickers for my computer, though. Poor case has an old Honda badge from my old Accord on it, Kicker stickers, Eibach stickers, my old Camry badges, and random other stickers I got in auto parts magazines...
Anyway, all this is just my $.02 USD