>>7805741Most decent wallpaper sites usually have some form of resolution option for you to select from, whether it's a drop down list, or a wall of buttons, and they'll usually cater to most/all of the common sizes of screen, so finding WQXGA papes shouldn't be too hard.
And of course you can also search for papes in your screen resolution in google (other much better search engines are also available) just by entering the resolution.
As for using an HD1080 pape on a WQXGA screen, the results would actually be the same as for a WUXGA screen, where, depending on the chosen option, the image would either fit the width perfectly but would stretch vertically, or you'd get black letterbox bars top and bottom, or the image would fit the screen height but crop the left/right sides.
And no, in terms of 'upscaling' generally an OS will just do what it's told and fit the image to the screen in the way you tell it to without doing any fancy processing to maintain image quality, so, depending on the image, the bigger the difference between pape resolution and screen resolution then potentially the worse the image quality, and more importantly how noticeable that degredation is, will be, but this applies whether the pape and screen are the same aspect ratio or are different.