images folder is inside theme’s folder.
But relative URLs do not work that way. They are relative to the URL not to the filesystem path. Your problem is here:
<img id="thinker01" src="https://wordpress.stackexchange.com/questions/74779/images/thinker01.png" width="120" height="163" />
If you look at the request (via HttpFox or other means) you will see that the browser is looking for the image at http://your-site.com/images/thinker01.png and not at http://your-site.com/wp-content/themes/your-theme/images/thinker01.png Don’t use relative URLs like that. Give it a complete path as you did with your stylesheet.