If you always have the thumbnails in the thumbs directory, and always have the full sized in the images directory, then you could hard code that into your template.
It looks like you started to use the format from my
blogstyles tutorial, and the method there could definitely be modified to fit your directory structure. Instead of putting the full path to the image in the "MORE" section, you'd just put the image name like this: photonumber.jpg
And then you'd change the main index like this:
CODE
<a href="<$MTEntryLink$>#<$MTEntryID pad="1"$>"><img
src="photos/bathtubwords/thumbs/<$MTEntryMore$>" width="100" height="66"
alt="<$MTEntryTitle$>"></a><br />
And the individual entry like this:
CODE
<img src="photos/bathtubwords/images/<$MTEntryMore$>" width="500" height="333"
alt="<$MTEntryTitle$>"><br>
Does that help at all? Let me know if I'm completely off track and I'll see what else I can write up for you

Kristine