usr << "You look like this: \icon[usr]!"
In case you are curious, that's short for:
usr << "You look like this:
<IMG CLASS=icon SRC=\ref[usr.icon] ICONSTATE=[usr.icon_state]>!"
(The "\ref" macro prints out an internal id number corresponding to a data object, but hopefully you won't ever have to use it.)
What can this be used for? How about an illustrated chat world that shows icons of players next to their outputted text? And since icons can be links (embedded between two \link() tags, you can even make clickable "characters"! The possibilities are numerous.
IMG.icon {width: 16px; height: 16px}
You could get 32x32 icons by overriding this rule, replacing 16 by 32.