Are the images all of equal length? If they are, an expression should do the trick. Something… like…
(assuming all are 2 sec images on a 30fps comp with a 4f fade)
Create a new black solid and put it as the top layer.
Set opacity keyframes at frame 0 to 100, frame 3 to 0, frame 57 to 0, and frame 60 to 100. This will cause the fading in and out to black over 4 frames.
Now Alt-click the stopwatch for opacity and write: loopOutDuration()
Click out and you’re DONE.