As it’s not really possible to show a visual representation of your item then using your avatar is probably the best next thing… as at least you’re getting brand recognition. Or you could have half a dozen or so different image for different categories. Like holly, snow and lights on your avatar for Christmas tracks, something spooky for Halloween etc etc.
The only other options would be to have the song name in the thumb… which could be a tight squeeze, and is slightly redundant (I used to do that). A graphic equaliser… which doesn’t really tell the buyer much. Or you could have a highly customised image for each track… which could be pretty time consuming without adding much value… like making a cover for a book, in a way.
I’d spend the time to make your profile avatar the best it can be, and go with that… for the brand recognition. Your’s is nice Carl, I like it. I think the text could be scaled up a bit though. I know padding is important in any kind of logo placement, but I think you can get away with it when you’re confined to such a small box.