by the way, one easy way to get a background of your liking to fit your panel size:
Download a high(er) resolution picture, like in your case 2560*1440, and select 'edit with paint 3d'.
Then use the select option, and you'll see exactly how many pixels your selecting, it'll show you in the program.
Then copy that selection, paste in an empty mspaint file, and voila, you've got something to start off with...