thanks for the advise, one of the site i visited instructed me to do the following:
1. Create the backdrop images. They can be bitmap or pixmap files.
2. Place the backdrops in one of the following directories. (You may have to create the directory.)
System-wide backdrops: /etc/dt/backdrops
Personal backdrops: HomeDirectory/.dt/backdrops
3. Choose Restart Workspace Manager from the Workspace menu.
and know what? it didn't work

any good suggestions? i already created backdrops directory as my personal backdrops. i also tried looking for the system-wide backdrops and it does not seem to exist
help.