Mythic changed icons in May 2007. There was such an uproar from players — some threatened to quit if Mythic didn't reverse the change — that Mythic quickly published a file that players can use to restore old icons.
(Actually the icons in the file are slightly changed from the original old ones.)
You can install old icons automatically with Mojo. That's the easiest way.
But if you prefer to install them manually, here's how:
1. Download this zip file.
2. Unzip the file into the ui/custom folder in DAOC's directory. If that folder doesn't exist, make it.
On DAOC's character selection screen, click Options.
4. Select Custom Skin for Interface: Skin Choice.
5. Be aware that after each patch, you may have to select Custom Skin again.
Mythic warns that "These old icon sheets will no longer be updated or officially supported by the Camelot team."
Reference: Camelot Herald and Camelot Herald.