Default wallpaper has common path across openSUSE, SUSE
We will be newly using png for the default wallpaper set on openSUSE Tumbleweed and upcoming versions of openSUSE Leap and Leap Micro.
The driver behind the decision is the unification of wallpaper paths with SUSE Linux Enterprise via a compatibility symlink because the format had to be the same. SLES and SLED have been using PNG since the last rebrand in SLE 15 Service Pack 3 and openSUSE has been using JPG up until now.
Using a common default wallpaper path allows applications utilizing wallpaper or similar system branding to be re-run on SLES and openSUSE without a need to be rebuilt.