Toad grabs Storm during their battle and throws her through a conveniently propped-open elevator door. He then pulls the metal pipe out and does his fancy Darth Maul twirl. But...who propped the elevator doors open in the first place, and why? There's no apparent reason for Toad to have done this.
Umm, you're missing the point. Why is the elevator door propped open in the first place? Toad can climb on walls and jump - he doesn't need to go up and down the shaft.
Also he might have used the elevator shaft as a means of getting into the building. I know he can jump and climb walls and stuff but there might have been some particular reason that he chose this way of entering and he's a mutant, he's on a different wavelenght to us so what do we know!!
Actually, Storm (in the canon) would'nt be able to do squat in the elevator shaft, she's claustraphobic.
As for why the elevator was open in the first place, it would make the most sense for Toad to have any and all routes available to him for a quick escape. I dont know much about the character, but he seems to be the kind of male that would go the extra bit to keep his exit routes open. Just in case.
With the door propped open, the elevator is disabled (safety mechanisms will prevent the elevator from moving if any of the doors--even one on a different floor--is open). So, it easily could be that Toad and/or the others propped the elevator door open in order to disable the elevator, which would then force the X-Men or any security personnel to use the stairs. Doing so would be a great tactical advantage, since it would (a) tire their opponents out and (b) control the direction of the enemy's approach.