I'm afraid the first answer below is not entirely correct. Only listings that have been submitted to us manually can be edited at this time. We receive the information for your listing (link below) from Century 21 and we display the photos that they include in the data feed they send to us and you'll notice that they display the same photo on their site at http://www.century21.com/property/index.jsp?ref_code=C21Trul
Please contact Century 21 to ensure that they update the photo for this listing on their site and within the data feed they send to us. Once they do so, our display will update automatically thereafter.
Go to your profile and
Click My Listings, or just use the pull-down My Trulia
Find the property among those there and
Click Update details below the photo
On the Edit Listing page you can remove the old photo and upload a new one