Hi, I have a bit of expierence with color and it sounds like you have come up with a good scheme. I have a degree in design and my mom is a florist. If you do powder blue or even Tiffany blue maybe platinum sash or silver acessories(shoes, jewelry). But make sure that you do contrasting flowers like shades of white roses would be beautiful- like a few dozen tied together in a bunch. - don't do alot of green leaves in the flowers that might clash with the platnum. And please do not do "Blue" dyed flowers to match. Whoever heard of blue flowers? Congradulations and Good Luck!