It could be a mistake, maybe an error on my htaccess because I activated a hotlinking protection, but I don't redirect 403 and 404 to sponsor, I do it to the main index of each domain. Let me check them all, but could you tell me on what site you see I'm redirecting or linking to sponsor?, and do you have a firewall in the computer on you are reviewing freesites?. I don't have one on mine and I had no problem to access to the images (I know Zone Alarm Pro hides the referrer)
Sample of one of my htaccess:
AddType text/html .shtml
AddHandler server-parsed .shtml
Options Indexes FollowSymLinks Includes
AddType application/x-httpd-php .html
RewriteEngine on
***this is the hotlinking protection***
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://(www\.)?anal-sex-lovers.info.*$ [NC]
RewriteRule \.(gif|jpg)$ - [F]
***this section is for my main blog***
RewriteRule anal-sex-lovers_([0-9]+).html bopost.php?post=$1
RewriteRule archives-([0-9]+)-([0-9]+)-([0-9]+) archives.php?blog=13&arc=$1-$2-$3
RewriteRule pages-([0-9]+) pages.php?page=$1
ErrorDocument 404
http://www.anal-sex-lovers.info
ErrorDocument 403
http://www.anal-sex-lovers.info