Hi, when I look at the title shown on the thumbnail, It doesnt really tell me what I am breaking. I dont know if you intentionally didn't add the 'pool ball'. Now if your audience are people wanting to break a pool ball they won't know this by looking at the thumbnail. Maybe adding this would make it better. The pictures of the ball, could it not be better to have a clear 3 D picture of a pool ball?
All said, I am not that good at thumbnail so lets wait for others to add to this. All the best.