Could get cans from the Mexican grocery store and roses from Costco? This seems like a pretty cheap way to bang out some colorful centerpieces... If you cut the roses short, I think they'd stay out of the way across the table.
I love love love this grid system for black & white photos - love the metallic frames too. I think we could do this in either the addition or the current home if we could find a space - maybe the kitchen above the hutch if we move the others?