I don't know if it's possible, but can you edit screenshots taken in Smash 3DS? I mean, if you find them on the SD Card on your computer, and edit it with MS Paint or something, it won't display on the 3DS. I think there is special data in the .jpg, which gets changed or removed when the image is edited.
And is it the same with Smash U?
And is it the same with Smash U?