I was doing some looking on the Wikia, and it turns out that new Grimm are going to appear in Grimm Eclipse. Here's a white Beowolf.

[hider=Because the image was so effing big...][center][img]http://vignette3.wikia.nocookie.net/rwby/images/4/41/White_beowolf3.png/revision/latest?cb=20150307223236[/img][/center][/hider]