68
You can do this quite easily!
In the post create a custom field called: "storyimg" and place the url of the img you want inside it.
Now in php block add this code:
$storyimg=$post->get_meta('storyimg',false);
#xoopsTpl->assign('storyimg',$storyimg);
in your template this code:
<img src="<{$storyimg}>">
and your done. Customize to your likeing!
I haven't actually tested this code so there might be some bugs to iron out.