exec-php plugin does what I want to do, with the small problem that the php code is still displayed in the post body..
Code:
<?php if ( is_home() ) { ?>
<a href="http://www.domain.com/?p=permalink"><img src="http://www.domain.com/xyz.jpg" border="0"></a>
some text
<?php } ?>
<!--more-->
image links to the permalink, image disappears on the permalink page, but above and below the image on the home page, the php code is visible. Not sure what that could be, being very thick when it comes to this stuff.