I love the hand-on-the-shoulder pose. In fact, I really enjoyed this whole sequence of comics between X and Zero. There's nothing that definitely says either of them is gay, but some of the things they do and say certainly make it seem that way. And yet, at the same time, it's entirely possible that they're just two guys that have spent so much time with each other, two guys that have saved each other's lives so many times and been in so many fights together, that they're just totally comfortable with each other and have no problem showing brotherly affection for each other. Even if it does make them look really gay.
Of course, one could argue that, as robots, neither X or Zero are really supposed to have any sexuality of any kind. I might concede that point, but that doesn't mean that they don't have feelings of any kind, platonically or not, does it? Besides, how can anyone explain all that X/Zero yaoi?