You can change the icons displayed next to nicknames in the Nick Panel of channel tabs. To change the nickname theme, choose → on the main menu. The Configure screen will appear. Click Interface to expand it, then click Nicklist Themes to display the Nicklist Themes screen.
Click to select the Nicklist Themes screen.
Select a theme.
Sample icons are displayed here in the chosen theme.
If you have downloaded a nick theme from elsewhere, click to install it.