With the collapse of the Democratic Republic of Afghanistan, the Islamic State of Afghanistan began, and its new rulers suspended the issuance of stamps. In 1996, the Taliban created the Islamic Emirate of Afghanistan, wrestling for control of the country as a whole.
Each year from 1996 until 2001, unofficial stamps were issued. The designs were professionally done, and include many animal subjects — birds, cats, et cetera — as well as several mushroom designs and other things. All of the stamps of this era have been declared invalid by subsequent postal authorities.
However, the ‘false’, unofficial stamps of Afghanistan have proven popular with a lot of stamp collectors. Stamps (and covers) from each of these years are generally available for sale in the marketplace. Check the current selection; it is updated frequently so check back often.