i seen a bank doing it, 4 example if u sell T-shirts on a site u make somehting like this and u give the first 3 winer each a custom t-shirt.
http://solutiimagice.ro/b0necry
this is how it looks like, i would like it to integrate to my new shop (i should finish it in 2 weeks) i hope somebody have an ideea how to make it.