I used places we have visited, Hawaii, San Francisco, Las Vegas, Texas, Los Angeles, Grand Canyon...
I bought theme paper from Michael's, for Hawaii - tropical flowers and parrots, for San Francisco - hearts (for I left my heart in San Francisco), Las vegas - I got a bunch of brochures and cut of pictures, put them on thick card board and pasted them to white paper. I then printed the name of the state on the paper and put it on cardboard. We put them in the table number holders (the reception hall provided) on each table.