I was thinking... (but perhaps I'm overlooking something and ZenPhoto already does this...) why not save the img filename while adding a custom title to an image?
For instance, let's say I have images of butterflies. ZenPhoto automatically uses the filename (before the extension) as the image title which is great. But what if I have a butterfly like the Platyptilia Carduidactyla or even with a longer name, then I would like to give it this name, but keep the filename to butterfly-231.jpg. This is easier if people contact you about a certain image.