Yes, there's a way. Back in the day, people made custom icons. I don't know anyone who's made some recently. Maybe someone has some old custom icons.
Customizations like this use the "data" folder inside the coh folder. For icons, you would need the subfolders:
texture_library/gui/icons/powers
And
texture_library/gui/icons/pet_commands
In those folders, you would place the specific icon files.