XDM's default Debian theme is really quite ugly right? I mean that background is just horrible. It doesn't do much for Debian's reputation for being a little bit arcane either. So I went to work recently on making a little bit more pretty. And found that the actual login dialog can be customized in the file /etc/X11/xdm/Xresources and the background can be set by creating a file /etc/X11/xdm/Xsetup and running an appropriate command i.e. xsetroot -solid grey30. I started trying to make the actual dialog pretty but quickly got bored. Thankfully even just setting the background colour makes thing a lot nicer imo. Just a little note.