yeah thing is you can't make it your default user pic - it doesn't save the image with each post, it just saves a pointer to "default pic" and then uses whatever your default pic de jour happens to be. one would have to leave the default pic as it was, then upload the new image with a different name and NOT use it as the default icon. save it as something else, "New user Pic" or something, then remember to set it to that every time one posts.