mod_rewrite and deep links

[snaefell]

Hi there,
i found some pages, that have set deep links to some of my pictures. Beside stealing my traffic the pictures are somethimes presented in environments, i don't like. If i use a .htaccess file with the following code:
---snip---
RewriteEngine on
RewriteCond %{HTTP_REFERER} !^$
RewriteCond %{HTTP_REFERER} !^http://((www|blog|foto)\.)?snaefell\.de [NC]
RewriteRule \.(gif|jpg|GIF|JPG)$ ersatz.gif [L]
---snip---
i can block these sites very well. Unfortunately also sites, which read my RSS feed like Bloglines.com (and which are wanted) are blocked. Has anybody an idea to solve this problem?

snaefell

[GeoS+]

There are some other interesting enviroment variables:

connection & request:

REMOTE_ADDR
REMOTE_HOST
REMOTE_USER
REMOTE_IDENT
REQUEST_METHOD
SCRIPT_FILENAME
PATH_INFO