Hm, OK, yes it is quite big.
Here are some things I tried that reduced the size to 150 kb and then 93 kb:
- set color reduction to selective
- choose a different number of colors. 256 is the default, but that's more than needed in this image (which is basically beige with some noise etc). It looked god at 16 colors (around 150 kb) and lost a bit but not much as 8 colors (which took it to 93 kb).
The same settings looked a bit nicer in Fireworks, and reduced the file to 70 kb.