For textures, head here: http://www.cgtextures.com

The textures available there are not seamless tiles, but you can use the Seamless Textures out of Anything tutorial available on this forum (I haven't the time to hunt it up myself at the moment) to make them tileable.

Fireworks' native format is PNG, so it will handle CC3 symbols quite well so long as they're not still packaged in a CC3 catalog. Still, the Dundjinni forums are very accessible and generally the best place to start looking for particular symbols and objects.

Also, don't underestimate the usefulness of Wingdings fonts for icons.