Go to the Add/Edit tab and select the desired listing from the drop down menu.
Click Manage Photos.
Select the photo(s) you want to remove by using the small boxes at the top of each photo, then click Delete Checked.
Click Certify & Save when you're done.
If you are removing photos from a listing you are marking Closed, remember that you need to keep at least one exterior photo on all listings except for Land, Business and new/proposed/under construction.