A mix of photographer photos and detailed images of any damage.
Use a mix of photos of you wearing the item, preferably photos captured by a photographer at the event you were wearing the item. This helps buyers imagine the dress on them and get a sense of how it fits.
Please include detailed images of any damage you note about your item. If buyers are aware of the damages and have seen them in the photos prior to purchase, this ensures there are no surprised when they receive the item and will reduce the risk of them returning it back to you.