OK I think it's a YVELTAL I REPEAT IT IS A YVELTAL .i had a feeling this picture was YVELTAL so I had to cross check with many yveltal pics and yeah I can guarantee you THAT it is yveltal, clearly . ( If u wonder how I am saying the picture is yveltal, then here is my explanation: the part of the pic which looked like claws to me(down left from the hidden text) had me thinking. So I looked through yveltal's pics and guess what? The above pic is yveltal showing the backside which is black whereas it's front side is red)
So yeah, so that's what I think about the picture. I may be right. I may be wrong.