If you have Lightroom 5.7 or Lightroom CC then you can sync your Lightroom images to Lightroom mobile which would also be available at www.lightroom.adobe.com
You can visit the above mentioned page from your Apple TV and view your images.
How to sync images to Lightroom :Adobe Photoshop Lightroom Help | Sync Lightroom desktop and the Lightroom mobile app
Else you can have your images on an external drive.
Please let me know if it helps.
I have an iPad, for example. I don't have an Apple TV yet. Are you saying that the Apple TV will recognize the Lr Mobile App collections on the iPad? Would you do this through AirPlay?
Regarding the external drive- I have put pictures on a thumb drive and plugged into BD player- used BD player software to look at pictures. In my home I could actually use a network hard drive and access that through something other than Apple TV. How were you suggesting to access the pictures from an external drive?
But other than this no server-based or computer-based way to show pictures and even better yet, slide shows?
Appreciate the help, John
The Lightroom mobile app collections are available at the webpage: lightroom.adobe.com.
So you can visit it anytime to view your sync images from your desktop Lightroom.
For better option you can mirror your computer screen via airplay to your HDTV.
For further information please check the below link: