I've run into several websites that use the "security image", and to be honest most of them I don't actually remember what they are until I see them. I can't choose the image myself, so one of them is something banal like a toaster. If I see the toaster, okay, I'm good. But am I 100% certain that if I see a banana instead that I'll say "Something is amiss here!"? I really don't know.

On the other hand, if I could upload my own security image for each site, I guarantee I would remember it, because I'd probably use something I drew myself.