This is about LXQt, don't know if other various Desktops affected, I suspect
something changed how openSUSE interfaces with DE wallpapers, maybe more.

LXQt - Incorrectly displays default openSUSE wallpaper on installation. Launch
LXQt Configuration Center > Appearance, is  set to the default "Frost" but
non-functional. Later although I found that clicking almost every other choice
did nothing, after clicking "System" suddenly selection was functional and any
wallpaper can be selected and applied. Compared to 15.1, noticed the removal of
the "Apply" button because selection is dynamically applied which made
troubleshooting a bit confusing because was an extra parameter to consider why
wasn't working.

Speaking of which...
I've watched various YouTube about 15.2 now, and one of the first things all
comment on is the default wallpaper. IIRC I think this wallpaper was introduced
sometime about 13.1? A more interesting wallpaper would have made a world of
difference, everyone is changing it out as one of the first recommended
configurations.