Pull down the Avatars menu, and choose Edit Identity. Your 'identity' window will pop up.  Click the 'personal' button and then press the 'change' button under the heading. Browse to your 'personal' folder, the possible images in that directory will be shown on the left panel. Select one as your avatar and press 'OK'.
Another way is the following:
Right click on your avatar (it has a blue frame around) and select 'edit identity' from the menu.
Your 'identity' window will pop up.  Click the 'personal' button and then press the 'change' button under the heading. Browse to your 'personal' folder, the possible images in that directory will be shown on the left panel. Select one as your avatar and press 'OK'.
You can get new and different avatars from sites on the Web (just use the ones on this web site or from the links that take you to the best sites).