We just booked our venue for our ~80 person wedding next April (YAY!!!), and it has a lofted space that overlooks the rest of the reception area. We already have room for all the necessities (food, bar, dance floor, etc.) and are trying to come up with some creative ideas for this space. The only thing I've thought about is a DIY photo booth. I'd love to hear some other suggestions! The space is approximately 17' x 31'.
Below are some photos from the lofted space looking down on the rest of the venue and one from the floor looking up at the lofted space.

Re: Suggestions for "bonus" lofted space at reception?
they used it a lot- cocktail hour, cake cutting, and it was terrible. Really crowded and hard to get up and down.
Love the photo booth idea, depending on budget maybe turn it into a lounge space with couches?
I would put something there that is targeted to younger people.
Totally agree to be careful about what you put up there, because people may not be able to climb the stairs (or may have trouble in heels and a dress after a few cocktails).
I'd also hesitate to make it a lounge space, because it's so separated and hard to get up and down that it would inhibit mingling. I'd be worried 5-10 guests would just end up camping out up there the whole event. I prefer a venue to encourage mingling not prevent it.
What about putting the band or DJ up there? And obviously your photographer can take some pics from up there. I also think a photobooth is a fine idea, because people would go use it for a minute, then go back to the party.
With an 80 person event in that huge space, honestly, I wouldn't use the loft at all. Maybe put a couple high-top tables up there, no chairs, so people can go up there and look down, take pictures out the back window, set down their drink while they're doing it, whatever. But with all that space downstairs, I wouldn't segregate the party like that.