This tip works in Gentoo linux but for sure might be adapted to work for any other distribution.
First, enter the directory:
create a symbolic link to the application you want to execute and the name that should appears in the menu:
ln -s <path>/<application> Name
ln -s /usr/bin/xbmc-standalone Xbmc
In my case, I ended up with:
ls -la drwxr-xr-x 2 root root 4096 Jan 4 18:36 . drwxr-xr-x 7 root root 4096 Jan 4 21:28 .. -rwxr-xr-x 1 root root 2404 Oct 5 18:03 Gnome lrwxrwxrwx 1 root root 24 Oct 6 17:56 Xbmc -> /usr/bin/xbmc-standalone -rwxr-xr-x 1 root root 2187 Dec 31 11:01 Xsession
After that just install xdm, gdm, kdm or any session manager you prefer and select in my case Xbmc as a window manager. Edit the file /etc/env.d/90xsession and put the line: