RunSubmit.com uses a 3rd party service called Gravatar to host your personal image. You need to get yourself an account on the Gravatar website (its Free!). Once you have an account there, you can associate one or more of your email addresses with pictures that you upload.

Once you have a Gravatar account, come back to RunSubmit.com and click on your user name at the top of the page (this takes you to your user page). Make sure that the email address you have entered in your RunSubmit.com profile matches the email address you used to register for your Gravatar. After a few minutes, your picture on RunSubmit.com should change to your new Gravatar picture.