There is even a Facebook app for Insanity Wolf.
Insanity Wolf can be seen as a "Chaotic Evil" character. He is usually shown to be a morbid and corrupt wolf who will commit acts of cruelty and insanity.
Although the Insanity Wolf meme began in 2009, the wolf image from which this meme is derived has been appearing online since at least 2006. On October 21st, 2006, YTMND user deathtoll5000x created OMGWTFHOLYSHI-! (WARNING: loud volume). This YTMND has under 800 views and is not responsible for popularizing the image.
The image also appears on vivcam6300's Flickr image stream, posted October 21st, 2007 and labeled "inter net pic"
The image has also been used in a 1999 printing of Sir Arthur Conan Doyle's The Hound of the Baskervilles.
A TinEye Image Search shows that this fierce wolf has been used as a popular forum avatar for a number of years. Given the immense presence of this photo and the different ways it has been used, it is likely that it is a commonly available piece of stock photography.