When using the Steam version of DisplayFusion Pro v8.1.2 to assign wallpapers, JPG files are being used instead of PNG.
Windows re-compresses JPG wallpapers and they look really bad.
Even if the source image is a JPG, they should be converted to PNG first.
I see that DisplayFusion is creating a PNG version of the wallpaper in:
%LOCALAPPDATA%\DisplayFusion\
However there is also a JPG version being created which is used instead.
