For the last 20+ years, since windows 95, maybe even further back, like Windows 3.1, I have always used a solid black background.
I will make a black bitmap the size of my screen resolution so my pc doesn’t have to use any computing power to stretch or rescale the image to match my desktop. I’m sure stretching the image takes no meaningful overhead today, but on a 386/16 with 4mb ram, and a 256k Oak Technology VGA card, rescaling or stretching your background slowed down how quickly a window can appear or be minimized.
Before that, I used MS-DOS, which has a black background by default.
Out of habit, I still create a black bmp the size of my desktop for my background.