Launch xmonad from KDM and set wallpaper

I’m a bit confused, though I might just be being a doughnut…

cat /usr/share/xsessions/xmonad.desktop 
[Desktop Entry]

This works fine to launch xmonad from KDM. And once inside I can “xpmroot ~/background.xpm &” to set my background. The xmonad instructions (xmonad : a guided tour) state that you should set that in your .xsessions or .xinitrc, but I don’t want to set things globally for X - I just want to do it for xmonad. I tried pointing the Exec line to a script that does both, but it doesn’t seem to like it.

How should this be done?

I’ve read this thread, and it seems to imply it can’t be done.

Add New X Session - openSUSE Forums

Is that right?

Would I have to drop KDM, and use different start scripts from a CLI login? This seems odd…

Well, I just set it in .xsession, which works OK.