having 2 different backgrounds is easy to do, no matter what version of windows you are using, even with different monitors that have different maximum resolutions.
basically what displayfusion is doing... takes 2 images and makes one new image and tiles it.
you have 2 monitors
your main monitor is directly in front of you
your secondary is on the left
the image for the left monitor should be place to the right of the one of your main monitor, then save and set it in the display manager to tile, dual wallpapers done without a tool. just photoshop or even the windows paint will do fine.
my set up is 2 different monitors, the max resolution for my main monitor is 1280x1024, my secondary is 1024x768.
if you have a set up like this, then just add the width together and use the height of the main monitor for the image height.
so make your image 2304x1280 and set your images in the correct position save and tile.