My idea would be quite involved to implement. It is easy enough to control smart lights or add audio in a command, but to add video is not as straight forward and is a more advanced task. I would like to see native support for images, gifs, and videos within a command. It could be something as simple as what we have to do to add an audio file to a command but with a few more options to set the location the image or video displays on the screen. Maybe there could be an option for random location too or even an option to display multiple different images or the same image multiple times in different locations with different scales. Also with a few tweaks to the overlays feature in lumia you could easily implement it into the streaming software.
While not being served up natively by lumia stream, if you use OBS you can create scenes that include video, images, or animated gifs that can be turned on and off with twitch channel points.
By creating it as a scene, it gives you control over where you want to display it on screen and how many instances.