I don't know if this website infringe copyright or not but it has a lot of wallpapers in whatever resolution you desire even in Ultra HD.
The website is Hdwallpapers.in and you can download as many high quality wallpapers as you like for free from different categories there.
There's no need to pay someone just to find some hd desktop wallpapers. There are no watermarks or other restricting images in the wallpapers there.