It's a really nice thumbnail! There's plenty to tell me what your content is about.
1. I see your "S" icon in the lower left. It might be better if it were consistent with your current "SC" icon.
2. As a non FPS person, I wouldn't know this were Battlefield 4 if you hadn't specifically told me
. (BF4 fans please don't give me a hard time. I am horrible at FPS games ><.) Perhaps put "BF4" somewhere in your thumbnail?
3. Great border! I see you're taking advantage of the TuberTools materials
. I have limited access right now as a first timer who's trying all the perks out, but I like the style!
4. I'm not sure if it's just me, but the title looks a little tilted. It probably isn't as noticeable when it's on a phone.
I've noticed in my own initial attempts at creating thumbnails that you may or may not want to anticipate the playback stripe as it may block some of your text. If you ever do playlists like I am for my uploads, you might consider pushing your text to the left so that it doesn't obscure it.
Just wanted to be thorough. It's a cool thumbnail!