Accessible Images via CSS or JS

Hi,
  I assume this has been broached before but many images (and not
just peripheral ones) are not inserted via HTML; Whether due to insertion
via CSS or JS—or CMS limitations—it is often difficult for me to give
images meaningful alternatives.

  I am familiar with accessible image replacement (normally positioning
textual content 'under' the image or making it ".visuallyhidden," etc.) but
I am unsure if it is actually equivalent and it isn't always feasible to do
so.

  I'd appreciate guidance and direction but I also have an idea: many
digital images are named programmatically and without human meaning (e.g.
IMG457394573.jpg) but if I take the time to review and rename the image
then it probably has at least a modicum of meaning.

  I propose a standard that, as a last resort, allows alt text to be
derived from file names. I assume, it can be programmatically determined if
a file name is a 'lowercase-series-of-words-from-the-dictionary.ext' (.ext
being file extension). Shy of that (which language? what about slang?...)
perhaps it could be as simple as '
name-of-file-*ALT*-self-portrait-of-adam-powell.ext'
(underline added for emphasis).

  I am not familiar with any methods to create specific alt text attributes
that will carry over from other languages/systems (again, CSS, JS, various
CMS), but it would be really cool if there were.

  I appreciate feedback, pointers, explanations, etc.

Thanks.

*Adam Powell*
Learn more at my website:* *Adam Infinitum <http://www.adaminfinitum.com>