Here are some images I use: https://www.dropbox.com/sh/9gzzhm0fbtxb5d9/AACsRM8IwatPM2R9BDFVzb87a?dl=0

They are photo manipulations done by a Chinese artist named Yao Lu. They are photos of dumps in china, altered to look like classical landscape paintings.

I set the image to scale to fit the screen then change the awkward blue fill that desktop settings creates to be the same white in the frame. It makes it looks seamless and really nice. I personally have the desktop rotate between all these photos to add a little dynamism to my desktop.