Why don't you just upload a pic to all of your ads on behalf of your 'brother in law' or your several 'friend(s)' or whoever to help you sell the items? Or save yourself the time and trouble and get your 'friends' to register on the forum themselves to sell whatever it is they want to sell?
People are not obliged to buy anything just because they request a photo from someone they don't know from a bar of soap selling an item on a public forum.