I think from left to right we have... Flandre Koishi (what with the closed eye+hearts) Yuuka (because flowers) Nue (probably, looks like a ufo on her neck) Mokou (...who is in the middle of regenerating.)
EDIT: whoops, source page pretty much says it outright
Hm kinda disturbing but from an artistic standpoint I absolutely love it, its morbid yet does something interesting. I mean all these (aside from mouku maybe.) Are usually characterized as being kinda crazy, and if were going on the Post pc-98 games (Starting with EoSD)Then they all sprout from flan's level of crazy. Heck I just hope it doesn't get deleted, its kinda cool