https://512pixels.net/projects/mac-os-9-5k-wallpapers
My favorites among these are the gradient-rich desktops that dropped in Mac OS 8.5 back in '98, like those UFO ones.
That's when the OS gained support for icons with 24-bit color and 8-bit masks, which are the direct ancestors to today's 1024x1024 32-bit app icons. Perhaps to commemorate this full leveling up of the classic Mac desktop to millions of colors, Apple hired a small team of designers to custom make the UFO, Capsule and Tub desktop pictures.
Screen sized gradients between two relatively close colors almost always land in the sandbar of banding or dithering in order to quantize all those subtle variations to the limited color depth. But these desktops do a beautiful job at avoiding that. I'm not sure, but I think they achieved it by color grading a zero-to-255 3D render with a high bits/channel ratio in Photoshop, tuning the grade and quantizing to 8 bits per pixel from time to time as a sort of gamut warning. Any problematic areas could then be "buffed out" with careful blend mode shenanigans on the boundaries.