I tried to set a background for any object type which are supported by this attribute, but failed, it works with solid colors only.

I explored Style Sheet example and tried to apply any part of the code taken from Style Editor window, no luck.

At first I thought that I messed up with resources and a path for the image file, but I'm sure doing right.

It looks that Qt Designer just doesn't display the style, until it would be put into the application