Title pretty much says it all. Right now you can only use static images as your blank image for when a game isn't being captured. Being able to use GIFs would be pretty nice.
If not that, then at least the ability to make the blank image transparent so I can have a GIF in my streaming software behind the Dxtory capture.
I wanted the same thing. My solution was to set the colour to something that basically will never be in any game and then chroma key it in obs.
(https://i.imgur.com/XmhXuhM.png)