On the Accounts page on Polkadot-JS, your accounts are represented by DOT icon avatars. 

If you don't like them or would like to shake things up a little, you can change the icon theme on the Settings page

Open the drop down menu of the "Default icon theme".

Then select any of the themes. We are selecting "RoboHash" in this example. 

Don't forget to click SAVE after you selected the new theme. 

Then navigate back to the Accounts tab and you will see your new RoboHash icons: