Ok, I'll try to do this later.
But this would not overwrite people's individuals avatars (if they HAVE already uploaded their own avatar), would it? Because that's not what I want... only for people who have not uploaded their own image.
Also, do I write the full path like this
CHANGE U_Picture U_Picture varchar(150) not null default '#http://www.something.com/image.gif#', - is this correct?
Thanks for your help!