I have a Google Nexus 7 2013 version. It's a hands down great device with a great display. I also love to change the wallpaper on the home screen regularly.
Problem is I wasn't able to figure out the perfect wallpaper resolution for the device. I used 1080p photos but at the lock screen, a bit of the screen space is left out, which was annoying for me.
So I found a simple solution. Rotate the device in landscape mode and then set the wallpaper from the "Settings" menu as you would normally do. Go back and lock the screen now and rotate it to portrait mode. The wallpaper should take up whole screen space.