Weddingbee boards

I've been thinking of something like this, too.

I know I've seen a few ideas around the hive and the interwebs in general:

-a little card or 'ticket' at each place setting

- a sign announcing the photobooth

 - a sign pointing towards the photobooth

In any of these, you could easily add a little small print about it being 'complimentary'.

Have fun!

Specifically how you word it may depend on things like whether you're having double prints  and having people paste the photos into a guestbook (because then your note could urge people to remember to do that).  But you may not even have to get into the issue of trying to tastefully phrase, "Don't worry, we've already paid for this" - if your photobooth package includes unlimited photos, which is what it sounds like from your post, I think your note could include something like, "Take as many photos as you want - it's unlimited!"  You wouldn't even have to address the cost issue directly.

A cute way of introducing the photobooth in this card or note could be something like, "When you need a break from the dance floor, check out our photobooth!"  Then you can talk about props, double prints/guestbook, or whichever direction you're going with the photobooth.  :)