http://assets1.ignimgs.com/2015/01/0...jpg-7f7769.jpg
This is a preview from the upcoming Warcraft Chronicles book that's coming out later this year (and yes, the preview was publicly released). C'thun is looking absolutely monstrous, and is at least 1000x bigger than what we saw in game (ancient aqir kingdom looks like it spanned across the whole of Silithus as well, and maybe Tanaris and Uldum as well). One question remains, how did the titans bury something of that size? (Yogg is assumed to be the size of Northrend, but up until now we never saw official art of Old Gods' true forms.)