There are several things you can do to raise the value of your listings. First and foremost is, expose and promote the often over-looked features and benefits, and other hidden-value. With that in mind, always present you value-adding evidence in the highest quality format you can afford.
Display high-quality photos of your listing and area photos of local points-of-interest. There are mug shots and then there are glamour shots. One adds value while the other does what mug shots do. It cost the same amount to post a high-quality photo as it does an average or poor-quality photo.