Stickers

Just found some lovely blue stickers and a thermal printer on ebay that will be great for rewards when a correct guess is make (or perhaps a wrong guess too).
I'd like to give everyone a sticker with different images/ text depending on if they got a correct guess or not, but don't know the numbers of visitors, reels hold 1000 stickers...

The blue stickers would also encourage people to wear them and perhaps make it easier to spot repeat visitors...?

I've ordered some nice blue and also some yellow sticker to be used as "rewards". I've been trawling ebay for a thermal printer, I think I've found one, identified a Zebra/Eltron with SERIAL port or USB.
The serial port will do me just fine, so next I need to work out how to connect the microcontroller to the serial port, the article link here is the clue as to how to do this.
http://blog.codeblack.nl/post/NetDuino-Getting-Started-with-RS232.aspx