During an event from Dwango for announcing a new gaming event which I covered here:
http://www.neogaf.com/forum/showthread.php?t=934426
New OP, Please read carefully as not everything are allowed, and this only applies for Japan.
Not everything has been clarified yet.
Nintendo announced on a stream that videos featuring their games properties
uploaded to Nicovideo.jp is allowed. So far, they have acknowledged it for Let's Plays, Game Music Covers, and Fan Art.
Nothing else.
Under a Creative Endorsement Program
from Nicovideo (Dwango), which rewards video creators for making high-ranking videos, Nintendo will allow videos using Nintendo properties to receive such prizes.
There is a list of titles which they have not revealed for which the Creative Endorsement Program can be applied to, so it only applies under these titles. The program will be activated on 1st December, so expect more details later on.
Source:
http://nviewer.mobi/player?video_id=sm24939536 Skip to 7:26.
Here's an article from a news site about it:
http://www.4gamer.net/games/999/G999905/20141117079/
Questions linger:
Does this policy only apply in Nicovideo JP and not Youtube? How about the International version of Nicovideo?
Are LP's, Fanart, Music and Song covers only allowed? How about other works?
Is the same stance acknowledged by NOA?