my theory of whose hands are in the picture

The hand with wristband and red fingernail: Most likely, Remilia scarlet, Although, maybe it could be Flandre Scarlet's instead.
The Hand with white elbow gloves: almost certainly Yakumo yukari's hand, the probability that it is Kana Anaberal is very low.
The hands that holding a camera: it's Shameimaru Aya and no one else.
the hand with white sleeve: it could be anyone, but I say it's Kirisame Marisa, she's wearing a white shirt after all.
the remaining hand: honestly, I have no idea, it could be any character that Reimu knows.

tremolo_measure said:

my theory of whose hands are in the picture

The hand with wristband and red fingernail: Most likely, Remilia scarlet, Although, maybe it could be Flandre Scarlet's instead.
The Hand with white elbow gloves: almost certainly Yakumo yukari's hand, the probability that it is Kana Anaberal is very low.
The hands that holding a camera: it's Shameimaru Aya and no one else.
the hand with white sleeve: it could be anyone, but I say it's Kirisame Marisa, she's wearing a white shirt after all.
the remaining hand: honestly, I have no idea, it could be any character that Reimu knows.

here the answers
the pic is inspired by the song わんだーらんど・でさくらいぜーしょん featured in newest diao ye zong's album.
your guess are right for the most. the list is (according to songs in the album):
Flandre
Alice
Aya
Yukari
Marisa
Basically the album is about how people put their eyes on reimu too much she called that invasion of personal privacy