Is it possible to copy the appearance of all npcs in skyrim with the sliders etc? Or do the bethesda created npcs have specific details? I tried to make my character look like vilkas but it wasnt really working out.

It would be a shame if it couldnt, because some npcs look definetely a lot better than my created characters

Try this:
http://www.truancyfactory.com/mods/skyrim/skyrim_characters.html