That's what I've been doing lately. Most of the textures have been upgraded to 2k or 4k resolutions with parallax mapping, and I've overhauled more areas of the game than I'd care to list here.
I'm only pushing it as far as my PC can go until the game becomes unplayable, so far I haven't gotten there yet. Indoor areas are still a solid 60 FPS most of the time, averaging around 30-35 outdoors and only dipping to 20 in wide-open areas with very long distance views, so it's still completely playable and I'm still trying to improve it further.

















Click any of the images for the full 1920x1080 screenshot.
I'll take requests if anyone wants to see a certain part of Skyrim.