The banner shows either an image of a champion that the player has defeated, or the number of champions that the player has defeated in roman numerals. The banner carrier's examine text changes depending on what banner he is wielding. To change the look of the banner, the player can talk to the banner carrier.
If the player calls the banner carrier, a leprechaun's face appears on the banner for a split second. This is probably a glitch.
There was a bug where if the player faced the Grand Exchange booth and summoned the imp, he would appear inside the booth with the bankers and Grand Exchange clerks. He could not move unless the player moved away far enough so that he would reappear next to the player. This has been fixed.
When the player asks the banner carrier whether he is getting tired of carrying a banner around, the banner carrier tells the player that another imp replaces him when he's tired, and that the player didn't notice the last time he got replaced.
Snow imps had the same chathead as the banner carriers (in different colours), but theirs was updated with the 2009 Christmas Event. The banner carriers still have the old chathead.