Netscape 4.77 shows a placeholder icon for not yet fetched images (a curled sheet of paper, with colored shapes on them), what is then gets overdrawn by the loading image. Currently Mozilla 0.9.2 Build ID: 2001062823 on Linux-i386, but seen on others too. It would be nice, if the image's size is known, and is smaller than 29x32 (the icon used in NS4.x), then it should either scaled down, or be replaced with the same icon from NS3.x. I don't know its dimensions, but I remember it was definitely smaller than the "broken image" icon. I suggest the 4xp keyword at least, maybe nsCatFood for users with slow connections.
*** Bug 89578 has been marked as a duplicate of this bug. ***
This seems like a dupe of bug #41924
I think so as well -- 41924 is titled "... broken images", but deals with use of alt text and icons for other cases as well, including this one. firstname.lastname@example.org, reopen if you disagree. *** This bug has been marked as a duplicate of 41924 ***