you could probably add an instance variable and call it Playerwaiting and give it 3 numbers, 0, 1, and 2.
set an hour glass sprite that has two animations, 1 blank, and 1 with hour glass animated "or leave it as a plain non animated sprite" and name them blank and waiting.
set hour glass over both player icons in the default blank so u dont see the hourglass.. set an event up so that when its variable is 1 , pick unique id of which players hourglass you want to activate,, set the animation to waiting, , then when player is done with his turn have it trigger to 2, do the same for the other player and have an event that makes the hour glass go back to blank when its not the said players turn.
i hope this helps, maybe you'll get an idea from it even if it doesnt , good luck !