The third is the only one that looks interesting to me. ^^;
Although I think it's mostly because the other two give off the same vibe of "aren't these characters fun and wacky and random?? Look, there's so many colorful, fun and wacky random characters in this story!! Wouldn't you like to fall in love with this fun and wacky random world?? P-please...???"
...Basically, they feel like they're begging for the reader's attention in a very amateurish, unsophisticated way. Which makes me not want to give it. :T
On the other hand, the third cover actually seems to have been made with some level of artistry. The cohesive color palette, the mysterious lighting, the focus on one well-drawn character rather than a variety of rough designs plastered all over the space. And the glow of the blade placed right underneath the title, drawing your attention just as your eye finishes scanning down the image: "whoa; wait, she's got a sword?! What's that for; what could this story be about??"
...It's a classic case of 'less is more'. ^^