The Gravatar URL used by Stash appears to always return a "default" image for some users.

My users have all created Gravatar accounts, however Stash still shows "white heads on grey" for everyone but me. (The same is true for them, they only see my avatar). Here's an example of what the page looks like:

This is the image URL generated by Stash: http://www.gravatar.com/avatar/ee194f150caf4ef175b36caaeb2f7782.jpg?s=48&d=mm

When I visit that, I get the "white head on grey".

If I manually remove the last bit of the query string &d=mm, then the correct image is shown:

http://www.gravatar.com/avatar/ee194f150caf4ef175b36caaeb2f7782.jpg?s=48 produces:

My avatar URL works even with the extra &d=mm parameter: http://www.gravatar.com/avatar/811bf781347cfb9f8d6c74e355a843d9.jpg?s=48&d=mm

I don't know if this is this your problem or Gravatars ...