The rune also resembles a rune from diablo. also there are further things.
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 Tongue)
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 Birthday of Diablo, more better to announce here.)
For more check out
Count down to diablo Its speculation, but its fun none the less.