I'm Not really sure if this is the best place to ask this question but logic tells me it is 
I'm Trying to change the login screen for OpenSuse the green Screen for something a little bit more of my liking, and I think the only way to do it perfect and right is through the command Line, do not take my question as a priority question at all, this is just a preference i wanna be able to change, your time is quite appreciated 
I've tried myself this multiple times and foun nothing but :wall:
Configure Desktop -> (Under System Administration) Login Screen
Take yourself off of Themed mode and then choose a background wallpaper.
I'm thinking that's all there is to it? (assumes KDE kdm and menus of KDE desktop)