Hey I.R.
The splash can be set easily left, center, and right, and top, middle, and bottom. To offset it from center, which it sounds like what you want, you need to create the splash to the left or right of center on your template. Then you need to go into the uifile and move the userpanes right or left to where you need them. The shutdown button will follow the userpanes.
A quick example, lines 517 and 518 in a default splash uifile:
element sheet=styleref(toppanelss) id=atom(toppanel) width=139rp layoutpos=left/
element sheet=styleref(toppanelss) id=atom(toppanel) width=139rp layoutpos=right/
The widths are set equal at 139. If you set the left width to say 79, and the right to 199, it will move the userpane 60 px to the left.
There is a lot of trial and error making the splash offset and then getting everything else to where you want it, but that should give you a basic idea.
You can always email me with questions or send the logon so I can help you out. That should give you a bit of an idea though.