I'd assume it would come down to the image/icon. The module 'should' be able to handle 16bit.

Minimal suggestions:
Load as few modules as possible,
use as few images/icons as possible,
use solidcolors,
dont use a popup (the more menu's and sub menu's you open up the more RAM that gets chewed),
setup a custom install (so your only loading things you need)

ps: Are you running windows 95? (ah the memories... :D )