Islamic art is by it's own definition is quite strictly non-religious, while some in the west insist on calling it "Islamic" (in the same absurd way why Indian numerals are known as Arabic numerals in the UK) it was anything but "Islamic" in the religious sense of the way. Islamic art is the art that prevailed Islam's ban on art naturalistic and depictive arts, allot of Hindu, Buddhist and even Pagan motifs that built on their abstract nature to survive as non descriptive/naturalistic art which was heavily focused on geometry and symmetry which has already existed in the regions that Islam has spread into, like Mandala https://www.google.co.uk/search?q=Mandala.

> at worst you're insulting a religion which currently has 1.6 billion followers

Nobody is insulting anybody. This "criticism/discussion of something mildly related to some religion == insulting billion of followers" needs to stop. You certainly don't speak in the name of 1.6 billion people either.