I know "image" is a bit vague but it already has precedence as in "ISO image", and conceptually it's correct:
Image (ISO) => CDR(W)
Image (software) => Phone with EEPROM
How much sense does burning a CDROM to a CDRW make? The same amount as flashing a ROM to a phone.
"EEPROM Image" would be correct and I wouldn't be surprised if that's what it actually was, and then instantly got abbreviated to just ROM, because no one would want to say "ee-ee-prom image". Pretty much like almost no one wants to say "Guh-nooo-linux" - too many syllables.