Please support this request by adding a note to the Bat Wishlist saying that you want this feature. Currently there are at least 2 threads requesting this feature. You should put your request in both of them. I would also like to see it, just like Thunderbird has a "show images" button for each separate email.
One discouraging note, the original request for this feature was made in September 2003, and this "wish" hasn't even been assigned yet. So, either the developers don't think it's important enough or maybe it's too much effort for them to do. What makes an email client great is to give the user choices. I would love to have this choice in The Bat.