I currently have image files removed from my web site to conserve
space. Instead of editing the static HTML file, I want to use
.htaccess to redirect missing images files to a default image file. My
reasoning is that in the future, I may upload those missing pictures
again.

So, if I have HTML that says: <img
src="http://domain.com/images/blue-widget.gif"> and the file is
missing, it would instead redirect the image and load the default
image, http://domain.com/images/default-image.gif
(err.. I assume the static HTML would not change?)

Thanks,
Sun818

p.s. I am looking for specific code that I can plug into my .htaccess

What you are aiming to do would be possible. You could have your
standard 404 error page be a PHP script that can rewrite out an image
if that's what was missing. However, speaking as a Google Answers
Researcher, I would note that this information is a bit more valuable
than the $2.00 you have as the list price.

Then don't answer it.