Nice idea... Not sure about the space on the left, meaning it is a lot, but then it does represent the long journey ahead for the couple, so it kinda fits. I agree the color in the the inset might be better, but then what are "wedding colors?"
Yeah i dunno. Perhaps switch the colours about between the outer image and the inset image.
Get two canvases made, one large one for the outer image, then a canvas for the inset image.. stick it on and have the '3D' effect to it.. something different i suppose.