A new default wallpaper, which will be used for the new KDE SC 4.10, was pushed to the KDE GIT repository today:
The new default wallpaper animates the default KDE look & feel and is definitely an improvement from the previously default greyish background:
|KDE SC 4.8 default wallpaper|
According to the KDE SC 4.10 release schedule, KDE SC 4.10 release candidate 1 should be available tomorrow while the final release is expected on January 23. KDE Plasma 4.10 will also introduce a new default Air theme - for more information, see THIS post.
You can download the new KDE SC 4.10 wallpaper from HERE (click the link for the resolution you want, then click "background.png", right click the wallpaper and select "Save image as").
via the Google+ KDE Community