When the November update rolls out for all Xbox One users, it will include a custom background feature. You can make backgrounds from Achievement art, or you can create your own.
Major Nelson has shared a template (that requires Photoshop or something that reads .PSDs) in order for users to create their own backgrounds. You can find that template here, it automatically downloads after you click the link.
Once you toss your own image in its specifically noted layer in Photoshop (minor skills are necessary here), you can follow these directions as they’ve been provided by Major Nelson.
Connect a USB to console / Connect a source through DLNA
Launch Media Player (either directly or through Setting > My Xbox > My background > Custom image)
Navigate to source of your choosing (USB/DLNA)
Navigate to folder/file of your choosing
Select the jpg/png image – see it full screen.
Once you are viewing the image full screen, hit the menu button.
Select “Set as background”
You will be sent back to the full screen view of the image. Hit nexus, see the image on Home.
The gallery at the head of this post sports three backgrounds I made quickly with whatever higher resolution pictures I had on hand. I apologize for nothing at all!