Shoutbox

You would still technically need to apply a skin to do this, however you could just create a skin that adds in the appropriate images.

You'd need to edit the 923 and 947 definition files and add in an element like this:

<element  layoutpos=right content=rcimg(59000)/>

and then define 59000 as a new picture (the background you want) in your SkinInfo.xml

and then just apply the skin and it should just make those changes.

If you don't want to do it via skinning then you can use this script to change the background of the contact list, but not the logon window