The ATV remote has 7 buttons
Two additional functions can be assigned to extended presses of the menu button, and the select button. At the moment doing an extended press of the menu button brings up the download menu in this Add-on.
Here's a link to the Joystick.AppleRemote.xml that's used for the Apple Remote:
In a slideshow an extended press of the select button is assigned to the info function - which is why I thought it might do it in this Add-on. It doesn't, but it might be a good choice of key to use if you were to assign this function to a keypress
EDIT: The on-screen info can be toggled by a single press of the select button on the ATV remote when viewing individual pictures. Info cannot be toggled with the ATV remote when selecting which album to view, but a full view of the photo depicting the album can be seen by entering the album and then switching off the info panel.