Changing the desktop preview image on start screen

So I am currently using two monitors (1920x1080 for my main one and 1440x900 for my second one) and I wanted a different background for each monitor. I found a source that said if you edit the two backgrounds into one picture and then set the mode to "Tile", it will work. And it did. Two Backgrounds (Working) - Imgur
So now I am faced with the preview of the desktop on the start screen (when set on "Wide"). Look at the Desktop app - Imgur
It would be preferable for it to only display the 1920x1080 wallpaper instead of the clipped version with both of them partially included and the blank space above the 1440x900 wallpaper.
Thank you!

It is easier that you download a free version of https://www.displayfusion.com/
This will allow you to set different background on each monitor.