The early Muslim coinage copied the designs of the coinage of the Sasanian Empire the Muslims had overthrown as the local population was familiar with the design.
Although the Muslim coinage carried Arabic inscriptions, the old designs were retained, sometimes even to the point of retaining the images of the Zoroastrian Fire Altars.
(Note the coin at the right hand side with the Fire Altar image.)
These designs remained in use for approximately 200 years and, gradually, the Islamic coinage rid itself of all "graven images".