Are there theories on how those images get in there, what determines the order they are displayed in or anything else in general about google images? It's obvious in most cases (not all) that the 1st few results are images named to match the search term exactly, from pages with relatively high pr, but that is not always the case and in many cases the apparent relevenace of the results deteriorates pretty rapidly after the 1st 10-20 or so results. In all cases the search results do not even remotely correspond to the total number of images named to match the search term from high pr pages that are indexed by google. Totally innapropriate images almost invariably start showing up by page 2 or 3 and images you would otherwise expect to be right at the top don't show up at all. There does not appear to be any process for "submitting" images to be included.
I thought it was all about the alt tags, myself. It's weird, though, I keep getting hits for the same few images out of hundreds on my site which are all tagged in a similar style. I think there must be other forces at work.
I did a search and read through the previous discussions about this. The consensus seems to be, put the image in tables with an appropriate filename, alt-tag and surrounding text and that nobody really has a clue how it all works, other than to agree that it is pretty lame overall. Seems to me they just tossed it into the mix a while back and haven't bothered to really make it a useful tool, strange considering how many people go online specifically for the purpose of finding images.
As far as I can tell, this really isn't good practice but I have a large number of small images on one page, with CSS used to arrange them into a larger image - no alt text is used since the page is designed to make sense if the images do not display. alt="" is used to pass HTML validation. None of the images are in tables. Each image file however does have a descriptive filename - blue-widget.jpg for example, and after 2 updates a number have started showing up in logs as search results under the filenames on images.google.com