I have 4 themes installed (rockstar, anchorage, liquid and the new custodian) when I select any theme it show blank except for anchorage and it does not have the same lock and feel as in the theme manager. So I did image rendering with no success.
I am using newscoop version 4.4.6. Here's exactly what happens. I have several themes installed and the assignment to publications work ok. The problem is when I set up an issue and then select a theme the default template directory for that theme does not show. I can go back and forth between themes and it will only see the template directory for the empty theme. to double check I then go to themes manager for rockstar and rename the template article.tpl to article_rock.tpl and save. I then go to publications issue and select the rockstar theme but when I select template I don't see the article_rock.tpl but article.tpl. I tried this on your demo site and I was able to see the correct template.