If you are working on openSUSE itself:
1) Checkout git repos containing branding:
http://gitorious.org/opensuse/desktop-data
http://gitorious.org/opensuse/kdebase4-opensuse

Otherwise, modify the tarballs in place for package kdebase4-openSUSE:
2) Update desktop wallpaper:
Copy wallpaper from source to kdebase4-opensuse/branding/root/usr/share/wallpapers/openSUSEdefault/contents/images

Make sure you update all sizes!

If KDE is sharing a wallpaper with other desktops, it probably comes from desktop-data/usr/share/wallpapers/

Update kdebase4-opensuse/branding/root/usr/share/wallpapers/openSUSEdefault/metadata.desktop with the wallpaper name and author's details.

3) Update the image used for the background of apps' about pages:

branding/root/usr/share/kde4/apps/kdeui/about/body-background.jpg

This is another 1920x1200 JPEG so you can probably copy the large wallpaper.

4) Update the KDM theme:

branding/root/usr/share/kde4/apps/kdm/themes/SUSE/Background.jpg 

is the background image but you may wish to change the theme completely, in which case other files should change.

Note that the theme name, 'SUSE' is set in the kdmrc so if you change this, update it in package kdebase4-workspace

5) Update bookmarks, feeds, and other desktop configuration

These are stored in 

branding/root/usr/share/kde4/config/SuSE/default/

and contain a number of SUSE and KDE-specific URLs

6) Start button icon 

Can be replaced with 

branding/root/usr/share/icons/oxygen/*/places/start-here-branding.png

7) Application Defaults:
7.1) Kickoff application launcher
branding/root/etc/kde4/share/config/kickoffrc
sets the Kickoff's home URL and default Favourites

7.2) Login splash screen
branding/root/etc/kde4/share/config/ksplashrc
sets the theme name and the theme is contained in 

7.3) Oxygen settings
Eg windeco stripes are enabled at:
branding/root/etc/kde4/share/config/oxygenrc

7.4) Plasma settings
Are configured the oldfashioned way by overriding the config file using 
root/etc/kde4/share/config/plasma-desktoprc
Note that this configures the default desktop containment.

7.5) SUSEGreeter background
greeter/pics/background.png 
is the background for SUSEGreeter, the info page shown on first login.  Update it using the current background.  It is currently made legible for black text by adding using a Soft Light layer filled with white at 75% opacity in GIMP starting at 40 pixels.

7.6) kio_sysinfo background
svn://anonsvn.kde.org/home/kde/trunk/playground/base/kio_sysinfo kdebase4-openSUSE/sysinfo/kio_sysinfo 
contains the sources for the ioslave.  If you look in the kdebase4-openSUSE sources, you will see there is a kio_sysinfo_background.png that is copied into the install tree to replace upstream's version of the SUSE branding with the current openSUSE release's image. 

The image is currently made by fading the top section of the default wallpaper to white using a Dodge layer.

FINALIZING.

A script in the git tree, update_rpm, creates the source tarball for the kdebase4-openSUSE package.  It will either check the git sources out into a temp folder and use those, or use your checkout.  If you have local changes which have not been pushed to gitorious, set MY_KDEBASE4_OPENSUSE_CHECKOUT to point to your local clone, which makes update_rpm copy the sources from there instead of gitorious.

Commit your changes to your local git repo, go to your checkout of the kdebase4-openSUSE package (NOT the git checkout) and execute update_rpm - osc status will show that the tarball is modified.  Now just update the package changelog and osc ci.

APPLICATION CONFIGURATION