I actually like Bluegrass myself. It's like an alternate color scheme to the default. But I'm not thinking of changing the default style. Just to add styles.
About Black Wrapper which is the 3rd one. It probably doesn't look as good because it comes with a border. As you can see in the preview here:
http://www.styleyourforum.com/preview/index.php?styleid=645The problem with that is the border is formed by header and footer code which is separate from the style code. So if I put the border on, it would display all the time even on different styles. I'd like that style more if I was able to put the border on it without it affecting the whole site look.
I'm still looking into some other styles. Also, some of the styles have their own images for old posts/new posts and all that so that's a possibility.
For the Night Wolf style, I'm able to change the background picture on it.
I think that's it for now.