As there seems to be a couple of old free Xbox Live Avatar items being reposted, how about something new? This is the prop you get with the 2100 MS Points from Play.com, but without the points.
Go to http://www.computerbild.de/gutscheinaktionen/cbs-xbox-Banshee-Avatar-5828278.html?action=register
and enter an email address
If you don’t want to use a ‘real’ email address, go to mailcatch.com/en/disposable-email to get, yup, a disposable email.
Enter the email address that should be auto-generated for you into the box on computerbild.de, just copy the address, don’t click on it yet. Check the box and click ‘Code anfordern’.
On mailcatch.com (you should have it open in another tab/window), click on the email address and it should take you to the inbox where your code should be waiting for you to enter either on your Xbox or on Xbox.com.