This mod does exactly as it says, it replaces any invalid image references with the default no_image.jpg file. If you use a no_image.png file, you can use that also, simply make sure you put it in your /image/ folder and either rename or delete the no_image.jpg file, and it will automatically use the no_image.png file - This works on the whole of the catalog and admin sides, and even works if you've renamed your admin folder

Note this has only been tested on 1.5.X but the code should work on all of 1.4.X versions too