image rewrites with .htaccess - is it even possible?

We all know that it is possible to rewrite dynamic html files to php files,
but is it possible to create dynamic jpg files?

i.e. rewrite a fictive 22.jpg to 1.jpg?

yes
You could also rewrite 22.jpg to 22.php and have your php script output a dynamic image if you wanted.

On a lot of my sites i've had picture query strings similar to this /93-new-audi-a5-3.0-tdi.jpg which would be rewritten to /images/93.jpg
That way I get keywords in the image url for Google Image Search lovin'