The answers by the other professionals on here have covered most solutions. Your agent who has the listing needs to log into their MLS and update the pictures for you. MLS automatically syncs with several real estate sites, but usually takes 24 hours to update, every evening around midnight I believe. Your agent's company website most likely feeds from MLS. After MLS is updated all the other sites should be current. If there was an ad placed directly on a real estate website, you may have to amend the ad manually on the specific website to override it. Hope this helps!