I’ve made a number of my images available as free downloads sized for smartphone and desktop computer backgrounds and wallpapers. They are licensed under a Creative Commons attribution license and can be used for non-commercial purposes.
View and download the more than 25 smartphone wallpaper images at: https://ryandavison.github.io/wallpaper/phone
View and download the more than 20 desktop/laptop computer background images at: https://ryandavison.github.io/wallpaper/desktop