I would like to know if my photos will ever turn up on Google Images?
How can I ensure that they will or wont appear?

turning mod-rewrite on along with utilizing your robots.txt will help your chances.

if you turn off mod-rewrite and disallow access in your robots.txt then it will be less likely.

a quick example of a robots.txt file which i have on a site.

User-Agent: Googlebot-Image
Disallow: /

User-agent: *
Disallow: /zenphoto

What does
`User-agent: *

Disallow: /zenphoto`
do?

What he is saying above is
Googlebot-Image can NOT get to his whole website

all other "SearchBots" can get to his website but not the zenphoto directory