No matter the size of the room that your wedding reception is in, chances are that there is plenty of room for a photobooth. all it takes is a bit creative placement of every item you bring.
the picture below was taken in a smaller venue and we were backed up next to the buffet tables, barely enough room to get by but we made it work. the printer is inside the booth and the props table was next to the booth.
at the most, we could get 5-7 people in the booth and for most of the crowd that was plenty.