Does this wedding dress look too much like a costume to you?

I think it's really pretty, especially given the setting you've described. To make it look less costume-y, I'd probably eliminate the hood. I love the drapery of the arms and such. It's so dramatic. I don't think this dress next to a suit would be awkward by any means either. If you love it & your fiance loves it, I think that makes it even more special :]