Still haven't got the radio WPS patch to sync nicely, in the meantime there is a new interim build up which supports custom splash screens.
A splash screen has been blatantly stolen for this from Julius who does the jbuild for Ipods (and resized a little for the H10). No splash screen is included for the 20gb.
For theme designers - simply place a file "splash.bmp" in the root of the player (ie, not in the .rockbox directory, the very root) to use this as the splash. It is not resized, and must be the native size of the screen. It is also not settable via any means other than replacing that file. By removing that file, the normal rockbox splash will be displayed.
5gb:
rockbox5gb20071203.z ip
20gb:
rockbox20gb20071203. zip
Master Patch:
master.patchdec03.zi p
EDIT: I'm also going to have, as standard, a couple of days before I update the original post and the thread on the rockbox forums in case I miss godawful bugs.