Data, data, data. Words and numbers, graphs, and figures. Necessary in our work and lives, but we all need a break from looking at these things. Though it doesn't contribute to your efficiency or enhance your workflows, desktop wallpapers provide a nice break for your eyes. Apple has always provided great desktop pictures for us to use, but it can't hurt to have more.
Here is a link to a site with some beautiful hi-resolution images to enhance your desktop: Pexels. Right-clicking the loaded image in your browser may give you the option of using the picture as your desktop image.