I couldn't find a 4k version of the anniversary wallpaper, so I upscaled the no logo version posted by u/ItsJeremyJenkins for those anybody else who might be looking for a 4k version. :
1000+ The Elder Scrolls V: Skyrim HD Wallpapers and Backgrounds
The Elder Scrolls V Skyrim 5k, HD Games, 4k Wallpapers, Images, Backgrounds, Photos and Pictures