I can only go by my one experience writing a wedding toast, but I think the best way to write a touching and above all unique toast is to tie it in to something having to do with the wedding- any scripture or literary readings, the words to a song, or, in my case, the couple's honeymoon destination, which happened to be Egypt.
I mentioned a little detail of ancient Egyptian culture, their belief that putting something into writing made it real. I then applied that to what the couple had just done- putting their committment to each other into writing. I wrapped it up with that classic Yul Brynner line and even got some of the other guests to chime in with, "So it is written, so shall it be done."
Of course, you can't go wrong with simplicity. Describe the bride in glowing terms. Describe the groom the same way. Declare them a perfect match.