This is a list of files needed by PhotoPost for normal operation:

data/*
forums/*
help/*
images/*
languages/*
stylesheets/*
templates/*
uploads/*

addfav.php
adm-admlog.php
adm-approve.php
adm-backup.php
adm-cats.php
adm-cfgtpl.php
adm-cfgedit.php
adm-cinc.php
adm-db.php
adm-editcfg.php
adm-inc.php
adm-index.php
adm-main.php
adm-menu.php
adm-modcom.php
adm-move.php
adm-options.php
adm-order.php
adm-pa.php
adm-photo.php
adm-templ.php
adm-userg.php
adm-users.php
bulkupload.php
comments.php
config-inc.php
dcfp_auth_lib.php
ecard.php
editphoto.php
footer.htm
header.htm
header-inc.php
image-inc.php
index.php
login.php
login-inc.php
logout.php
member.php
pclzip.inc.php
pp-inc.php
register.php
reportphoto.php
showgallery.php
showmembers.php
showphoto.php
slideshow.php 
uploadphoto.php
useralbums.php
usergroups.sql
watermark.php
zipndownload.php

The following files are only needed during the install or upgrade process and should be removed when you have finished:

CHANGELOG.TXT
email-inc.php - obsolete, used to overright old files, can be removed entirely
fixmedium.php - used to upgrade pre-3.0 PhotoPost
install.php
photopost.sql

UPGRADE.TXT
upgrade.php
upgrade252.php 
upgrade252.sql 
upgrade306.php 
upgrade306.sql 
upgrade310.php 
upgrade310.sql 
upgrade311.php 
upgrade311.sql 
upgrade32X.php
upgrade32X.sql
upgrade33.php
upgrade33.sql
upgrade40.php
upgrade40.sql
upgrade41.php
upgrade41.sql

upgradecats.php - used to upgrade pre-3.0 PhotoPost

These files should be left if you plan to import Usergroups:

usergroups-phpbb.sql
usergroups-phpbb2.sql
usergroups-vb.sql

and, of course, this file filelist.txt and CHANGELOG.TXT files do not need to be uploaded.