I did what you said about xpice, but how do I launch "debwm xfce wmxfce" on an icon like icewm ? Or if too complicated to explain in which terminal should I launch it ? (because when I input "debwm xfce wmxfce" in a debian chroot terminal, it tells me command not found and when I launch it from a 0S2008 terminal the host window appears, sadly, debian and xfce do not follow ). Maybe I should put something else too in the wmxfce ? I tried to replace "icewm-session" with "xfce-session" and "startxfce4" (the command to start xfce on a normal computer)
Xephyr :1 -br -screen 800x480x16 -dpi 96 parent `wmctrl -l | grep -i icewm | awk '{print $1}'` -ac &
openwindow.py xfce4
debwm xfce4 wmxfce