title: Rails: Assign users a random default avatar (ala Twitter)?
body: <p>I'm using <a href="https://github.com/thoughtbot/paperclip" rel="nofollow">Paperclip</a> to handle avatar's for users and currently set a default image using:</p>
  
  <p><code>:default_url =&gt; '/images/img-missing_:style.png'</code></p>
  
  <p>But what I'd like to do is when a user registers, give them a random avatar that they get until they upload their own.</p>
  
  <p>Twitter does this with its "egg" avatar and that have probably half a dozen different colors that get assigned.</p>
  
  <p>How can I accomplish this?</p>
  
  <p>Note, I'm not wanting to show a random avatar every time a call to the user is made, rather I want them to be assigned a random avatar when they register and have that one stick with them until they upload their own.</p>