On Search Enging World they said, "Do use descriptive short alt tags for your images - many search engines will use them (which adds to your keywords). Each search engine has different criteria for indexing your site (as detailed elsewhere; but, all don't mind the alt tags and some use them - go for it, its a free bonus)"
Now this I knew, but I got to thinking. Load, to the limit, each alt image tag with as many keywords as possible (of course relavent to each image).
Two things though. First, what is the limit relative to SEs? Second, does this cause a back lash from SEs?