Depending on where you live, you can try Googling "photo booth rentals" and your city/state to see what may be possible! If/when I ever have a big bash, I'll go all out!
Oooh, I forgot to mention that one way to eliminate a major seam is to use one long rectangle that is folded in half so that the fold is on the bottom. This works if your pattern is such that nothing appears "upside down." Stripes and repeated geometric patterns are good for this.