Well, I could give you a huge list of sites like this (since it is a part of our internet youth culture,) but I will only direct you to one site (a friend of mine,) at www.dreaminfinity.com ... there ya go.
Thanks. I found the cluster of buttons on http://www.dreaminfinity.com/htmlversion/main.shtml . Although I see the style you mean, I think those are fundimentally more artistic than the ones you presented. The backgrounds do contain some imagary (e.g. the eyeballs) and the text is other than a simple thin font.
In keeping with that genre, how about a background that's gradiated from blue to brown top to bottom, with a camel, all made as a "background" image. Then words, Like "PerlMonks" in a fat font with slight 3-d effect or edging to make it obviously the foreground.