From what I can see, it definitely has a "Hobbyist video maker" vibe to it, which isn't necessarily a bad thing. Definitely better than the modern soiface thumbnail meta. That said, I'm gonna go off your most recent iteration:
>>51001991A few personal nitpicks. First, the grass background feels a bit "busy", almost a bit too attention-grabbing. Not sure of a definitive silver bullet fix for it offhandedly, though. Additionally, it could eat up a bit less space on the thumbnail, at which point the text could more comfortably sit in the upper-left part of the thumbnail without chewing into both the "grass" part and the game screen part, which would likely remove the need for the gray background on it, and thus could just have a black border, akin to what's done with it on
>>51001952 Past that, you could probably squeak in each episode number on each thumbnail somewhere, but I can't really think of much else past that.
Overall, though, not bad. Might get around to watching these tomorrow.
Full disclosure: My thumbnail work isn't really great either, so take my advice with a grain of salt. 
