Your icons (actually almost all graphics too) live in /home/QtPalmtop/pics and /home/QtPalmtop/pics144. Most of them on the default rom are symlinks to /usr/QtPalmtop.rom/pics and /usr/QtPalmtop.rom/pics144 respectively.
To replace an icon, remove the symlink and copy your icon to /home/QtPalmtop/pics144.
To add an icon, just copy it to /home/QtPalmtop/pics144 and edit your .desktop to use the new icon.
Reboot to see the changes (actually there are other ways such as qcop QPE/System "restart()" and opening tab manager, exiting with OK rather than cancel.)
I've replaced most of the default icons with others and am currently in the midst of doing it yet again with noia kde icons, I'll post pics once I'm happy with the results.
OT - why is it that KDE has such a large amount of great looking icons but gnome doesn't seem to? Am I looking in the wrong place?
Stu