I have been thinking some about this. And I don't know exactly how this stuff works, but..
Old classic PS1 games with pre-rendered backgrounds looks horrible since they are such low resolution. So i thought about this... would it be possible to make a shader that takes all pixels and then copy them into maybe 2 or 3 or maybe even more? It's kinda hard to explain what I mean, but for instance if a image that is 100x100 pixels would then become maybe 300x300 wich would look nicer on a big screen. So everything pixel, or line bassicly gets twice or third as thick. I don't know if this is possible or if it would benefit anyhing though but it sounds to me that it could make things nicer.
*Edit - Isnt this what downscaling does..? Can a shader downscale..?