A scholarly digital encyclopedia focusing on Iranian Civilization. In additional to more specific entries about individuals, locations, etc, it also includes excellent broad entries on categories of art. See entries like Calligraphy, Carpets, Metalwork, and Art in Iran.
A collaboration between Google and cultural institutions around the world, this is a great tool to explore art with. Search an artist's name if you have one, or try exploring "Collections" using the Map feature or browse "Places" by country. You can also view any of these collections in a timeline to narrow down to eras that interest you.
Browse Artstor Collections by geography. Once you have picked a country of interest, narrow by date range or classification of art. It won't be 100% Islamic, but depending on the country, a large portion will be.
Great topical and work-specific videos and essays that can give you a solid start to your research. Some include short "Additional Resources" lists that you can use for the next steps in your research.
The Grove Encyclopedia of Islamic Art and Architecture by 
Medieval Islamic Civilization by