Is that DOpus 4 ?
On my system it looks into Sys:icons
for example: Sys:icons/drawer.info
or others like: Sys:icons/ascii.info
Edit: It's set in the DOpus 4 configuration under "System/Icons".
Maybe I should better change the icon locations from "Sys:icons" to "ENVARC:Sys" and use the normal DefIcons there like def_drawer.info, def_project.info etc. But my DOpus4 configuration is from 1993 and I was always too lazy to change it.
Read the DOpus 4 Manual guide file from one of the full versions like 4.16.