As a onetime specialist on the ‘Abbasid Caliphate, I thought it might be worth noting that the Islamic State's self-proclaimed "Caliph Ibrahim" is not the first Caliph to make his seat at the town of Raqqa in eastern Syria. That precedent was set by one of the most famous ‘Abbasids of all: Harun al-Rashid.
Although thanks to the 1,001 Nights tales, Harun is inexorably associated with the glories of Baghdad, the city founded by his grandfather al-Mansur, and he did indeed preside over the flourishing of the great city on the Tigris, he decided in AD 796, a decade into his reign, to move his Caliphal seat from Baghdad to Raqqa. The reasons are not entirely clear and may have been strategic, but he actually governed the Empire from Raqqa for the next 12 years, until his death in 809. It remained an administrative center for the western part of the Empire after the capital returned to Baghdad.
I doubt if "Caliph Ibrahim" will be the subject of songs and stories centuries from now. But then again, I rather suspect Caliph Ibrahim doesn't approve of the 1,001 Nights.