I'm not finding any websites that talk about using htaccess to deny all access to a directory (and below) unless it's an image file. Here's my best attempt:

<FilesMatch "\.(gif|jpe?g|png)$">
Allow from all

Order deny,allow
Deny from all

I have all of my back end php functionality in the admins/ folder. I want to deny everybody from calling those files directly through a browser to make it more secure. Those php files need to be ok to be included in the front end functionality which doesn't seem to be a problem. But, my admin images are in that directory as well (moving them out would be a nightmare). So, I'm finding that when I deny access to the directory, the browser can no longer display images from that directory either.

So, I was thinking deny all access to folders and files unless it's an image file. Is there a way to do that exception?