How to add or change desktop background in Calculate Linux Scratch 15 KDE Plasma 5?

I installed Calculate Linux Scratch 15 KDE Plasma 5 on my laptop. I cant seem to change the desktop background for some reason!! I have gone through the system settings and searched for solutions and hints for an hour. I also added kde-plasma-addon as suggested on the gentoo wiki.

Although, I like the default background but it would be nice to change it!! When I installed Calculate Linux 15 (both Mate, KDE version) I was unable to specify British English settings in the beginning of the installation process. I tried to change this after the installation, but I only got American English. It would be nice to have this option available in the future!! I installed LibreOffice and it chose en_US as the global option, I am however able to choose the UK English option for spelling etc.

Again I would appreciate any suggestion on changing the desktop background!! Thanks

You can change the wallpaper through the context menu on the desktop. (Alt+D, Alt+S) British English locale will be added to Calculate utilities in the future. If you do not find the option for the wallpaper changing, please attach the screenshot of the desktop context menu.