I am running Windows 7 Ultimate 64bit edition and have 2 x 27inch Samsung SynchMaster monitors and I was browsing through the windows 7 themes when I came across the Panoramic (dual monitor) themes. This got me curious so I looked a bit closer and found they will only work on windows 8.1. I really, really do not wish to upgrade to Windows 8.1.
First I will mention that the point behind the Windows 8.1 desktop themes is to display the panoramic pictures across two monitors in a dual monitor setup as a slideshow so if you are only using a single monitor you will not benefit from the following.
I did a bit of research to see if anyone had found a workaround and the conclusion was, not really. You can download the panoramic themes to windows 7 but they are not compatible so you will not be able to load them.
I found two ways on how to display or load the panoramic pictures in Windows 7 but they do not allow you to spread the pictures across a dual monitor setup. The first was using a zip file unpacker like 7zip to unpack the photos and the second (better) is a piece of stand alone free software called Deskthemepack installer which will install the themes for you the same as regular themes but you still will not be able to display the pictures across two monitors.
What I did in the end turned out to be very simple. First I used the Deskthemepack installer to load all 12 Panoramic theme packs into windows 7. Then I browsed to the theme pack folders and copied all of the panoramic photos to a new single folder which I created in my pictures folder and named Panoramic pics.
Now for the best bit. I downloaded the free 30 trial for Actual Multiple Monitors and installed it. I opened Actual Multiple Monitors and in the settings configuration background tab I added all of the panoramic theme photos from my new folder to the slideshow playlist. I selected the option for displaying a 'single picture over entire desktop', left the options for 'random play order' and 'search in subfolders' unchecked and set the 'change interval' to one minute then clicked apply.
Now I have all 120 panoramic pictures from 12 different themes as one slide show and it works just fine. Actual Multiple Monitors will cost $24.99 after the trail but you will get quite a bit more than just the ability to use the windows 8.1 desktop themes in Windows 7. You can add (any) photos to the list and display them across two screens although some pictures will look a bit odd stretched that far. If like me you have cameras that can take panoramic photos then you could make your own.
A could mention the other functions of Actual Multiple Monitors here but that is something you can look into and decide for yourselves.