Video Blasphemies

Something has been bothering me about all those execution videos that ISIS and their ilk keep posting.  Apart from the fact they are unspeakably barbaric and utterly repellent, obviously.  The thing is - and I'm prepared to be corrected here - as I understand it, the Islamic faith doesn't approve of representative art, as by producing an image of an actual thing is to mimic God's own act of creation.  Which would be blasphemous.  (Islam also forbids the worship of graven images, which is another reason why representations of Mohammed are considered offensive).  So, where does that leave all these Jihadists and their predilection for producing real-life video nasties?  What, after all, is a film or video other than a series of images which give the illusion of movement?  Aren't they, under a strict interpretation of Islam (and these groups, by their own admission, are supposedly flying the flag for the 'stricter' end of Islam), committing blasphemy?  Aren't they, therefore, bad Muslims?  Shouldn't they be beheading themselves (but not filming it, obviously)?

But this isn't the only example of the confused thinking of terrorists, who frequently, it seems, don't practice what they preach.  Take Boko Haram, for instance.  As I understand it, not only are they opposed to what they see as the corrupting influence of westernised education in Nigeria, but they want to take society back to the Seventh Century, an era before we were all corrupted by things like science, democracy and secular values.  The question, of course, id that if they are so enamoured with the Seventh Century and hate the present so much, why do they use modern firearms and other weapons to terrorise their victims?  Surely they should be using the technology of the era they want to go back to?  In which case they should be armed with swords, lances, spears and the like.  Then they'd be able to test whether the values of the Seventh Century are superior to those of the present when they came up against soldiers armed with modern assault rifles.  Sword or Kalashnikov - which do you think would prove superior?