I think I finally have this one figured out.
Taking this idea from http://www.theknot.com/:
And filling it with these flowers from http://www.fiftyflowers.com/:
I know it’s really “in” to submerge flowers and float a candle on top, but I have rarely been one to be trendy. For now I think we’re going to skip candles since the museum is very strict about having them contained.