You can add the logo you have uploaded to your store to the header that's appearing on your listings (via the listing frame option in Manage My Store) so it will appear on all listings, and you can also choose to show the navigation menu, which will show your store categories and people can click to go to other categories directly from a listing.
Other than that, you would have to add an image to your listings by hosting it elsewhere (eg Photobucket) and adding the HTML into the description (while in the HTML tab).
