I'm certainly no expert on weddings, but the Odaiba area gives a nice backdrop to a Central Tokyo wedding (I think) with the rainbow bridge, tokyo bay etc in the backround, you have the LeMerdian Grand Pacific and Hotel Nikko nearby along with some others.
http://www.meridien-grandpacific.com/
http://www.meridien-grandpacific.com/banquet.html
I hate to have been there if there was a minor earthquake at that couple's wedding!!!