Actually, I don't think that having a link from Photopost would be the best way to do it, because then you can only add one photo to a post. I'd like to be able to write a post, and add say 20 or 30 image thumbnails to it.
The code that you've entered above Casper, is the way I'm doing it at the moment... the problem is that in order to get the url to the image (i.e. data/x/thumbnail.jpg) you need to look at the page the thumbnail is contained on, view the source, and scour through it looking for the correct url.
Would there be any information in the PP database, that associates the showphoto number, with a thumbnail?