why is the guy just stood in the corner in the end?

For practical reasons it's a creepy image to end on. For storyline purposes I can't quite remember if they give an explanation, I'm pretty sure they mention that it's something that the witch used to do before killing her victims but I might be imagining that.

it's because it explained that when the witch killed the kids she "captured" she'd make one kid face the corner of the room while she killed the other kid, and then would kill the one facing the corner. therefore the cameraguy was facing the wall because the girl was getting murdered.

He's standing in the corner because earlier in the film the chick made a reference to an old story in the newspapers about a serial killer who kidnapped and murdered children (hence the bloody children's hand prints all over the walls) & while he was killing one in the basement he would make the other kid stand in the corner. The murderer later said the Blair Witch told him to do it. So the inference here in this scene is that the spirit of the witch is making these film-makers kill each other.