Ah! I thought that might be it.
I'm afraid my php skills are those of an enthusiastic amateur of the Google and "copy and paste" variety. However I would certainly try to assist in whatever way I can.
I have a sub-domain of my site, which is loaded in a sub-directory off the main site root. It contains a full copy of the main site and its own Zenphoto installation so in that sense I hope it mimics to some degree my live environment.
The reason why I had to define WEBPATH using http://domain was that the way it is set up in the standard release also includes the server root folder name, and this causes problems when trying to access data in the Zenphoto installation.
Thus I get the following results using the standard setup:
With this setup, using printRandomImages in a non-Zenphoto site page, I get the following page source created for each list element:
<a href="/public_html/zenphoto/divisions-and-regiments/7-signal-regiment/4sqn_7sr_1977_1980_0016.jpg" title="View image: 7 Signal Regiment"><img src="/public_html/zenphoto/zp-core/i.php?a=divisions-and-regiments/7-signal-regiment&i=4sqn_7sr_1977_1980_0016.jpg&w=115&h=115&c=1&cw=115&ch=115&q=75&t=1&wmk=!" alt="7 Signal Regiment" />
with the additional "/public_html/" construct giving me a page not found error.
The same happens with printLatestComments where the source code for each list element shows:
<li><a href="/public_html/zenphoto/brigades-and-squadrons/229 Signal Squadron/Berlin62.jpg.php" ....
(The latter having been amended to eliminate the second of my problems outlined above).
I hope this is clear, and please let me know how I can help with the DEV build.