Here is some of my .htaccess code for PutPhoto, I use subdomains, multiple variables etc, maybe this will help you.
rewriteCond %{REQUEST_URI} !^/index\.php
rewriteCond %{HTTP_HOST} !^www\.
rewriteCond %{HTTP_HOST} ^(.+)\.putphoto\.com
rewriteRule ^$ /index.php?display=user&username=%1 [L]
RewriteRule ^a/([a-z0-9_-]+)/([a-z0-9_-]+)/?$ index.php?display=gallery&id=$1&rndkey=$2 [L,NC]
RewriteRule ^i/([a-z0-9_-]+)/([a-z0-9_-]+)/?$ index.php?display=gallery&imgid=$1&rndkey=$2 [L,NC]
RewriteEngine On
RewriteRule ^uploadzip.html/?$ /index.php?display=uploadzip [L]
RewriteRule ^uploadzipstep1.html/?$ /index.php?display=uploadzipstep1 [L]
RewriteRule ^simpleuploadstep1.html/?$ /index.php?display=simpleuploadstep1 [L]
RewriteRule ^simpleuploadexisting.html/?$ /index.php?display=existingstep1 [L]
In use: http://gordon.putphoto.com/a/546/5631961