The MPO file format is simply a 3D container for JPEG images. The container holds Two Images, one for the Left-Eye and one for the Right-Eye. Thus creating a 3D image on compatible viewers. However, MPO files also have fallback support for 2D viewing. You can embed an MPO on a Website and a Webbrowser will treat it just like a normal 2D JPEG and only display the Left Image. 3D capable devices(like the 3DS) can open the MPO images embeded on a site and display them in 3D with no issue.
So essentially you wouldn't need to do anything other than allow MPO file uploads. You may have to block Image editing because a normal image editor will probably only export a 2D JPEG instead of the whole MPO. However, other than that, there is no reason you can't add support for MPO.
I right news articales and reviews on a 3D image forum and use Imgur for all my 2D image hosting(I pay for Pro) but I have to use my Dropbox to host my 3D images since no Image sharer supports MPO files. Using my Dropbox like this is far from desirable. So I would be very happy if I could upload my 3D images on Imgur as well.
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