I don't know if this will help, but we were on the Diamond 2 years ago, when she was only a few months old. What a gorgeous ship! I'm an architect, so I get really snoopy and stuck my head in the Wedding Chapel. It appears to be able to hold about 50 people, and is really attractive. I also saw the ship florist making arrangements for a special event. Don't know if it was for a wedding, but they were stunning, and not common in any way.
As previously mentioned, the Princess has the bridge and wedding cams, and out of curiosity, I've checked out the cams on most of their ships at one time or another (I said I was nosey
)and you might be interested in that. They usually leave up a still of the latest wedding, because you don't often catch one going on. In the very least, you will be able to see what the Chapel on the Diamond looks like. Good luck.