Pause the clip at a decent moment where a face shot is visible (or other recognizable feature if the face isn't shown). Then click the PrtSc button located to the right of the F12 button. Open an image editing program (paint, photoshop, etc) and hit paste. Save, then host at an image hosting site or attach the pic to a post. (Instructions from stevie).
Cut the dick out or something with an image editing program.