At the top of the page, there is a row of yellow buttons. Click on the left most button ("user cp"). On the next page you come to, at the top of the page you'll see a row of links with gray backgrounds, click on the "Edit Options" link. Down at the very bottom of this page, under "Other Options," is where you can change your avatar.
Thousand different paths
So many sterile ends
I chose the Devil's path
Never shall the sun kiss my face
And caress me with it's burning light
For I dwell in the shadows
And sleep side by side with death