I always wondered about the best way to do that. I like my wallpaper dark so I can see my icons, folders, etc.... better. Ever see those books that have black plages and white font? It would have to work like that for it to work for me.
The sequence was different for me since I didn't take the picture to make it my wallpaper. I was scrolling in my gallery when the image caught my attention. It made me remember a special memory so I figured that it would be nice to set it as my background.