I have recently been learning how to render in blender, i have experimented with a few things but this is the first one that i like, so i am looking for other peoples opinions, watermarked because i was also looking for watermark designs.
All feedback appreciated, please be constructive. 
It looks pretty similar to most other thumbnails I’ve seen on Roblox games. When I say that, I mean it looks very good, and is up there with thumbnails for more popular games. (I assume that this would be used as a game thumbnail.)
Design as a concept is very interesting. There’s actually a ton of principles and elements that go into something looking visually appealing. Though I’m no design expert, I have a few personal suggestions on the overall thumbnail:
I would make it more obvious that the avatar is attempting to guess the name of a song. (It’s hard to tell that he’s wearing headphones underneath all that Roblox avatar.) Perhaps adding music notes or a boombox would help with that;
Add some space between “Guess” and “That Song.” To me it looks a little squished; and
I would recommend a different color scheme. I did a quick search on other art styles for games of this type, and neon purple and blue were very common. Be aware that the colors you use can effect the “vibe,” so to speak, that players get when they first look at your game. This is coupled by the facial expression of the avatar, which gives me the impression that “Guess That Song” is intense and serious.
I hope this helped!
I like it! It looks very original and different from what I’ve seen! Although I don’t like the watermark and how it stretches across the whole icon. Is it just for this post or the final one? Other than that keep up the great work! 
