@archsimkat I think your suggestion, properly implemented, could make the thumbnails a lot more varied and interesting, but I'm put off by the amount of work that would require.
Let me explain. To do this right, I couldn't really focus on showing the map. I tried this and failed and here's why: most maps are square when zoomed out so either don't fit a 16/9 rectangle or get trimmed, which makes them a lot less recognizable. They also come in a dizzying array of colors which at some point will clash with other elements of the thumbnail but can't be altered because color pallettes are central characteristics of maps.
I came to the conclusion this might even be counter-productive. Map images just can't compete with robot battles and explosions when it comes to how visually interesting they are. To you, a map image might be meaningful, but not to any viewer unfamiliar with faf, and that's a wasted opportunity to make the thumbnail attractive to them, which is the whole point of doing promo work.
What about zoomed in, heavily recolored beauty shots? Going this route could potentially show off some interesting action that happened in that particular game. Unfortunately, there's no chance the twitch video of the game in question contains even one frame that achieves this potential and is uncluttered by unit icons or UI and framed such that the action is visible in the final thumbnail. That means I would have to hunt down each replay and make screenshots for this purpose.
In addition to finding good action (hard when you can't rewind the replay), I'd have to find a camera angle that works well after all the other text and logos are added. I'd have to then adapt the color and exposure corrections for each image.
I'm confident this would look great and would make the YouTube feed as a whole look a lot more interesting, but it's more than I'm willing to do in my spare time, partly because I'm nowhere near as good as Sid at wrestling with the game's camera so that aspect would feel very tedious to me. If there are any volunteers out there that are willing to help with capturing the screenshots, let me know. If I had help with that, and only had to do the Photoshop work, I might be up for it.