I noticed a weird symbol a few days on a boulder near the Krug's camp site on the blue side (those two rock neutral monsters or whatever they are), and when Riot announced the up coming champion, Bard ... the realization of what the symbol looked like dawned on me ... that it looks like Bard's face/mask.
...I would add a photo on here but all of my screenshots shows nothing but white.
I looked around the Krug camp myself, but couldn't find anything.
There are 5 of these symbols scattered around the map. Off the top of my head, I can only remember 2 of the locations: The one by Krugs that you mentioned, and one at the bottom end of the river, on the rocks adjacent to the bush in the river.
They were placed there as a deliberate teaser by Riot, though of course it was done in such a way as to give us no solid information whatsoever. Wouldn't be much of a "teaser" otherwise, now would it? They've been there for weeks, and since then we've had the official teaser for Bard, along with his official reveal and subsequent release on the PBE. And now we also have his cinematic. It's all part of the release process, in order to build as much anticipation as possible.
I can confirm this also that the Easter egg for Bard is in the map, they also play a sound like a magical pixie sound at around 1:50 ish something like that. 
It's magical guys!
