It’s a nice historical idea. I think the Middle age theme will be best. It reminds me a similar birthday party I had attended last year, which was very nice. The main attraction of that party was the coroplast they done according to the theme and the large posters showing the each stages of medievalism. I think these coroplast and large format printing services ( http://www.clubink.ca/gallery/coroplast/ ) are from Club Ink,Toronto. That was definitely not a tacky idea.