looking for a hack...
 

Is there a hack that can do the following?

When a new member registers on the site he automatically gets an avatar to identify him as a newbie?

No, but I can do it for you.

It actually requires just a simple template edit. Try putting this into your postbit and postibt_legacy templates:

<if condition="!$postinfo[userid]"><img src="url to your image" /></if>

Thanks, I will try that!