Come up with an assortment of KDE stickers for promo booth giveaways. Compare & contrast square-printed stickers versus die-cut stickers. Consider other promotional items (pens, sticky notes, etc.) as well? Let's list out what we find and what it'll cost, then bring in people from Promo for review.
3"x3" die-cut stickers (the K-Gear) from StickerMule are $351 (308 euros) for 1000 stickers. As suggested, these should probably be held back as special giveaways or for a small donation.