Almost every salon provides these for free or at a small cost to their customers (peeling off $1 at a time). It provides the most obvious way for them to see their results. They put them on the same spot every time they tan, providing a virtual "tan tattoo" of untanned skin under the sticker.

Most salons provide at least 4 different stickers, and many provide all of them.  Your customers will love them. With  1000 tattoos per roll, your cost is about one penny for each sticker.