Branch command is indeed the only way to do it. It's best to set it up in a Common Event though, so you can call it from anywhere.
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Then, you'd call it from your event. You'd set the variable "0001:FaceToShow" first, then you'd do the "Call Event" command. (Don't forget that you can set a variable to the value of a variable.)
Of course, if you only pick a face once a game (say, at the start), set FaceToShow's value at that time. Then, you'll never have to set it again.. you'd just call the Face Showin' event whenever you want the hero's face to appear!