Images etc.

How are the laws of using pictures from other, official websites?

Take for instance www.catchthesnitch.com I want to do something similar, but with another theme. What legal issues do I have to look out for?

As far as I know, you can't use images form other sites unless they're public domain - such as government sites. In all other cases, you will need permission or risk breaking the copyright.

Do you know what the chances are for getting permission to use them in illustration?

Doesn't hurt to ask. Really just depends on the site.