Adding Ending Slides

[Porcelyn]

So I made an ending slide for Rekke for the Rekke mod but neither of us know how to get it in game. Any ideas?

[Tarlonniel]

Specifically, while I know how to add an entry to the ending slides stringtable to accompany the slide,  I need to know where to put the reference image, what format it needs to be in, and what kind of entry I'd need to add to the .conversationbundle