I'm useing the same jpg for my KDM background, my bootspalsh background and I've also set it as the background in the Logon Mananger of Kcontrol. However after entering a password in KDM the whole screne flashes white for a second when it moves to the bootspalsh, is there some way to prevent that?

I was thinking that since they all use the same jpg for the background I could somehow tell the bootsplash and KDM theme there is no background and they will display there small changes on top of the login manager background. That possible?

Well, if you think the problem is that they all share a jpeg, just make three copies of that jpeg and point them each to a different one. Instead of feeding them all <picname>.jpg feed them <picname>1.jpg, <picname>2.jpg and <picname>3.jpg respectively.

thats what I'm allready doing, and I think the problem is that it unloads then reloads the jpg each time. What I want is for the background set in KDE's login manager to be background.jpg and for the bootsplash & KDM to simply put their small changes on top of the login manager background

Oh, ok. I understand what you're trying to do now. Unfortunately, I don't think it's possible - sorry.