If you've chosen to use the PowerStandings home page component in your Salesforce app, your reps will see an "at-a-glance" view of the standings bar in their standard side panel view.
Part of this component is a user profile view, accessible by clicking a hyperlink on the rep's picture, his or her name, or the small "person" icon on the upper-right area of the panel.
Users can upload their own profile pictures. These will appear in panels and leaderboards across PowerStandings.
To upload a new picture, click to open the Personal Profile page, on the Home tab. Click the Change Picture link.
You'll be given the option to use an existing Salesforce Chatter picture, if you have one, or upload your own.