This tutorial explains how to customize the background image of your Xbox One console's dashboard (homescreen). The procedure is simple and straight-forward, but it should be noted that some features are only available after installing the latest system updates.
Press the Menu button of your controller and then go to Settings. Select the My Xbox menu > My Background. Several options are available, you can choose from:
Solid color - choose a solid color from the color palette (default black).
Achievement art - achievement from your current games (you need to be signed-in).
Custom image - you can use an image stored on a USB key, a screenshot from one of your games or images from a PC connected to the same Wi-Fi network (synced with the Media Player app provided with your console).
Once you have selected the background image, go back to the My Xbox menu for more customization options such as Tile Transparency. Since the March 2015 update, tile transparency level can be adjusted to one of the following: Solid, Mostly Solid, Partly Transparent or Mostly Transparent.