Ah, uelsk8s you are right, thanks!
I did change the /usr/share/icon/default/theme file. I want it to work even before someone is logged in. A detail of course but an important one for me.
Still curious about who is controlling the login screen. Have problem following the start up procedure. Not important but still, can be useful. Have tried to find info but most site only goes as far as to the rc.S and rc.M scrips. Can't help to feel that this is a bit of a wizard secret.
Any wizard out there who would like too... ?