Does anyone know where I can download unflattend vector PNG's to use on my site?
Not sure what you're asking here. PNG is a file format that is the default setting for fireworks files.
Did you mean pattern? If so then I can help you because I have a lot of pattern to design website.
One gppd place to look would be http://www.vector-finder.com/
They offer mostly EPS (Illustrator Files) but you can convert it into a PNG for use in Fireworks.