I, along with couple of others I think, have been looking for this for quite some time. What I wanted is that when I right click on the desktop with GNome, I should see my entries in the default menu. I did quite some search on this but no luck. Finally today, I did it and that too in two ways.
Lets do it the Gnome way first:
Install nautilus-actions using the command
sudo yum install nautilus-actions
Now run the command
nautilus-actions-config
you will get the box looking like this:

Now click on New or Edit and you have the window like this:

Enter the label, tooltip and select a icon from drop down or select your own icon.
Select main in profiles and then click on edit.

Enter the path and parameters for the program to execute. Now, time to make it appear on the Desktop right click menu:
Go to advanced tab and add a new schema called x-nautilus-desktop and select it:

Now send a HUP signal to nautilus or log out and login to Gnome and see your menu in the right click on desktop 🙂
For the second solution, install openbox.
sudo yum install openbox
open gconf-editor and go to the key /apps/nautilus/preferences/show_desktop and unset it.
Login to Gnome/openbox and see the openbox menu instead. You can install obmenu to configure the openbox menu to your taste.