I noticed your reply about "can't stream anything via an Apple TV that isn't a file in an itunes lib."
You should be able to use an ATV with your Sony TV via HDMI cable and you can use it to display your iPhoto photos from your iMac.
Otherwise, the only way you can provide content to an ATV is through an iTunes library, either by syncing or streaming to it from the library. If you make your own files, you can import them into the iTunes library and then you can sync or stream them to an ATV.
You can also get content directly on an ATV from the iTunes store from the available content listed in the ATV menu (such as podcasts, movies and TV shows).