One other thing – it looks like @rrslssr is running a similar approach specifically for travel photos – and I want to share a tip.
My mirror runs a combination of some of my own travel photos and places I’ve been from Unsplash.
To make the modules more legible and pop better, I made a photoshop template. The top layer is a very light transparent to black (from the center) radial gradient. My backgrounds are the lower layer.
This applies a very light vignetting that is consistent among all the background images. I experimented until I found the gradient settings for the top layer that were perfect to my eyes.
I’m sure there are easier or smarter ways to add vignetting, but this works for me.