There was a need to get rid of that question mark product image in prestashop 1.6 (nobody likes seeing question marks all over their shop). So I replaced it with a camera image which is much better looking!
You need change the 404.gif file in the img directory because this is the image which gets loaded when presta cant find the product image which is generated by the product code (or id).s
This is what it looks like now! 🙂