Are you referring to a gravatar/avatar or blavatar? if so note that changing them is not an instantaneous process. The changes take time to propagate throughout the internet.
Below are the best practices for successfully uploading your Gravatar, Avatar and/or Blavatar images:
(1) Choose an image that does not have any transparency in it and scales both up and down in size without losing definition. Prepare the image prior to uploading it and make sure it’s 512 x 512 pixels or larger so it will look the best in the widest range of uses.
(2) The image filetype has to be either PNG, GIF or JPG. Make sure the file name contains only letters and numbers – no special characters – and make sure all letters are in lowercase.
(3) Also make sure the image file name has an extension (Example – image.jpg)
(4) Note that there is a time delay while your gravatar image propagates. If you are experiencing problems then go to the gravatar site and read the FAQs as it contains common questions and answers to them