The Photopost Integration for phpBB, Ubbthreads, VB3, IBP and IBP2 use CSS Integration. Meaning if the modifications are based on CSS wrapping images around tables then the look should be the same. However note we do not use the templates of those forums so if there is a HARD CODED template modification you would need to adjust our ppopen or ppclose templates.
Now alot of times if you have some CSS that is not looking just right it can be solved by editing the forum CSS and making the image url's full url's not relative ones. This of course assumes your issue is CSS
If you PM me a url to your board and admin login I can take a peek and give you some hints on what specifically your issue is.
As far as Demo's those sites rotate so I don't know what demo's there are but if you do an Internet Search on Powered by Photopost I am sure you will find Photopost integrated with phpBB. I have done lots of installs with phpBB.