There is no need to arrive in Iran weighed down with foodstuff and toiletries. Most essentials can be easily found in larger cities, and can be bought at reasonable prices.
Consider bringing an electrical plug adaptor, sink plugs, a flashlight, and a medical kit (including an adequate supply of any prescribed drug). Woman may bring feminine sanitary products. Do not forget sunglasses, a lip salve, a high-protection sunscreen and after sun lotion, and an insect repellent. You may also find a GPS or a compass, as well as a Swiss Army knife, in dispensable. Bring several books or a Walkman to help you get through the long, free evenings. You may also want to bring small souvenirs for your Iranian friends. Drivers may consider bringing spare parts for their cars.