This year the NFL changed the way extra points work so that 2-point-conversion attempts are snapped from the 2 yard line as they always were, but extra points are now snapped from the 15. If a team lined up from the 2 yard line (maybe the told the officials they would be going for 2) and kicked an extra point, is there a penalty? What if they attempt a drop-kick after snapping the ball from the 2?
There is no explicit penalty or foul in the books for this; that would be listed in Rule 9, section 1, in the 2015 Rulebook.
Rule 11, section 3, states simply that:
The Try begins when the Referee sounds the whistle for play to start. The team that scored the touchdown shall put the ball in play:
anywhere on or between the inbound lines
15 yards from the defensive team's goal line for a Try-kick
two yards from the defensive team’s goal line for a Try by pass or run
Note 1: A team's choice is not final and is subject to change following a team timeout or accepted penalty
Note 4: If the ball has been declared ready for play by the Referee, and the offensive team wants to change the location of the ball, they can do so by calling a timeout.
If it were to happen (that a team lined up on the 2 and then kicked the try), I assume the referees would simply prevent them from lining up to kick the ball. If a drop-kick occurred, it would possibly count as a personal foul - unsportsmanlike conduct (Rule 12):
SECTION 3 - UNSPORTSMANLIKE CONDUCT
ARTICLE 1. PROHIBITED ACTS
There shall be no unsportsmanlike conduct. This applies to any act which is contrary to the generally understood principles of sportsmanship.
It is not specifically enumerated in the list of unsportsmanlike actions, although the list is not intended to be exhaustive. I would surmise if this actually were to occur, it might be added to the list the next year.
Alternately, it's possible it would simply not count and they would lose the opportunity to re-try. Personally, that feels like the better option: the rules don't allow for a kick from the 2, so if you want to kick from the two, feel free, you just give up your point.
If a team attempted anything except a run or pass from the 2 yard after a successful touchdown during regulation, such as a placekick, dropkick or punt, then that 2 point conversion attempt would be deemed to have been unsuccessful.