The Channels feature has built-in caching, otherwise, there would have to be a request going to Facebook (and other streams you've configured) for every page load of your site.. which would really slow things down. You can control the caching time in the JFBConnect -> Configuration area.
As for posting photos, right now, JFBConnect only supports pushing a status update along with the URL. JFBConnect will set the Open Graph tags for your pages, which should include an og:image tag, setting the image to use in any previews for that page. We don't have support for uploading a photo to Facebook right now, as the recommended way is to share your page which already has the image.
I hope that helps explain, but if you have any other questions, just let me know.
Thanks,
Alex