One of my Ludum Dare "hacks" is to try and use a thumbnail that will attract "my" audience. So I try to show off a little pixel art which should bring in the folks who like pixel art right? It also hints at the type of genre, this looks like a retro platformer just from this thumbnail right? If you're looking for a 2D-Pixel-Art-Puzzle-Platformer, hopefully this grabs your attention. This thumbnail is also bright and eye grabbing... Maybe too bright? lol

I thinking that attracting the "right" players to your game should have a positive impact on your final score, since those folks are more likely to enjoy the style of game you're presenting and maybe give you more favorable scores!