Wish I could tell who that was waaaay in the back over there. Looks to me like Gilgamesh...and if you look close enough he has a nekoarc over his crotch...

Also is that Cornelius' top hat over by the watermelon? post #317467

two questions:
1.where is Arcueid?
2.is the person with very long hair flying in the sky, Akiha?

1. Arcueid is to Ryougi's left, wearing what looks like a clam shell bikini. Red eyes, blonde hair, and the style of the hair is much the same.

2. Perhaps an assumption, but I believe the one in the sky is Fujou Kirie. Since there are a bunch of girls alongside her and they are usually "floating"...or "falling" in this case. heh heh

Couldn't the "Matou Sakura" and "Gilgamesh" in the pic actually be Asagami Fujino and Cornelius Alba respectively?

It's possible, but it looks like she's wearing a ribbon, which would indicate Sakura.

Setting the source to the thumbnail of the actual post, because the uploader saved only the thumbnail. See huge-o-vision parent post for actual source.