Probier mal Folgendes:
Code:
RewriteCond %{REQUEST_FILENAME} !-f
RewriteCond %{DOCUMENT_ROOT}/bilder%{REQUEST_URI} -f
RewriteRule .*\.(png|gif|jpg|css)$ /bilder%{REQUEST_URI} [L]
RewriteCond %{REQUEST_FILENAME} !-f
RewriteRule !.*\.(png|gif|jpg|css)$ /main.php [L]