Textures do not scale. You can scale the patterns, however, and you can trick Fireworks into thinking a texture is a pattern. Here's how.
1) Click the Pattern fill button (FW CS6), or choose Pattern fill from the fill drop down list (FW CS5 and earlier).
2) Scroll to the bottom of the list of patterns and select "Other".
3) Browse to the FW Textures folder on your hard drive and click on the texture you want to use to select it.
4) Click on the "Open" button.
The texture will fill the object just as it usually does, but it will have the pattern adjustment handles.