Your logo seems fine to me (pretty cool, actually) so I assume the problem's been solved but still, here's the code to change the logo:
<style>
.logo {
content:url("insert direct image link here");
}
</style>
You can download the original logo here and then you can use any image editing app of your choice to do whatever you want with the logo (pretty sure you have to at least make it recognizable as the logo though, as per site rules). After editing, you can download the edited logo and get the image's direct link (I use this website for all my image links), where you just paste the link in the code above. Voilá, your own (kind of) handmade logo!
Of course, you can always just scavenge through Layouts for custom logos people already have made, too :o