Yep, people judge a story by its 'cover' all the time, a thumbnail is basically a reduced cover where you gotta say a lot more with even less real estate.
2 characters are definitely a must if the story is centered around their relationship, whether romantic or otherwise!
I do like your new icon! But it leads me to think it's a fantasy series with the wings, compared to the more regular/contemporary feel of the first icon. Unless that IS what you're going for!
Personally, I give a chance to lots of things regardless of how their icons appear; particularly with novels, since I know a lot of writers don't have a background in visual art/design.
But one thing's for certain: If I see a anime/manga/webtoon thumbnail, I'm expecting anime/manga/webtoon tropes for better or for worse.