Wake up, make breakfast, look at regular Monday-morning websites...
MMO-Champion: New Blizzard Game this Week End?
Wowinsider: More signs of cold on official sites
Worldofwar.net: Blizzard Image Solved
Of course, speculation is abound, as it was in previous Blizzard Teasers. The most creative piece of analysis has to be this from diablofans.com:
Original Theory by Diablofans.com, seen at mmo-champion.com
Another interesting fact is the URL: http://us.media.blizzard.com/232309/_images/ice1.jpg
Why 232309? If we assume that the numbers correspond to the letters in the alphabet we get 232309=WWI ... ring a bell? :-) World Wide Invitational
23 = W
23 = W
09 = I
Anyway the "hidden" picture is called 04.jpg. (http://us.media.blizzard.com/232309/_images/04.jpg)
My guess is that tomorrow we'll see a picture called 09.jpg, then on wednesday 01.jpg ....
Today is 04.jpg = D
if Tomorrow will be 09.jpg = I (if its not, maybe not diablo at all Smiley
Wednesday will be 01.jpg = A
Thursday will be 02.jpg = B
Friday will be 12.jpg = L
Saturday will be 15.jpg = O (June 28 WWI 1st Day, Good to announce here also.)
Sunday will be 3.jpg = 3 or three.jpg or whichever. = (June 29 WII 2nd Day, and B-day of Diablo, more better to announce here.)
Also people said it's definately WotLK related anyway. because of this pic: http://i31.tinypic.com/i44c43.jpg
[EDIT 25-06-08: With the Day3 Teaser is looks like this theory isn't valid any more, 23.jpg was the latest image]
This has the sort of feel of the SC:Ghost reveal some 6 years ago, rather than the leak-ridden announcements of the last couple of years. Looking back though the sense of anticipation was only matched by the sense of disappointment in what SC:Ghost was slated to be: a console FPS/RPG. With any luck my hopes will not be dashed once again.
The smart money has to be on an announcement about Wrath of the Lich King given the Rune analysis and overall ice theme. Other possibilities range from a simple Worldwide Invitational teaser to a massive bait and switch leading into an announcement for Blizzards much mooted 3rd project, codenamed Hydra.
Whatever the announcement, the next week is likely to be interesting.
EDIT: lol at me mis-spelling 'Blizzard'. Anyway, fix'd
More rampant speculation / gaming the theorists. These were posted on wowforum.gamona.de:
Whether it is or is not fan art, I do love the second shot.
EDIT3: Just a quick update to make sure that Diablofans got proper credit on the number theory in the block-quote. It was their original work.