user-agent: googlebot
Disallow: /*.png$

user-agent: googlebot
Disallow: /*.gif$

user-agent: googlebot
Disallow: /*.jpg$

user-agent: googlebot
Disallow: /*.pdf$

user-agent: googlebot-image
Disallow: /

User-agent: msnbot
Disallow: /*.jpeg$ 
Disallow: /*.PDF$
Disallow: /*.gif$
Disallow: /*.png$