After effects problem

ok ive got this background image that im trying to change but i cannot select the image at all. I didnt actually make the movie, im just updating it. there is only one main composition and then a bunch of png images, one being the one im trying to update. Anyone know how to fix it where i can select the old image and delete it? i dont see it on the timeline either which is odd. Im fairly new to AE :cantlook: