I’ve been waiting for something like this to turn up: Pattern in Islamic Art is a browsable collection of 4000+ examples of art (chiefly decorative art, obviously) from across the Islamic world.

Now I realise that there’s no shortage of this stuff on the internets generally, but this site also includes page scans of scholarly works which analyse the geometry employed in some especially fancy designs. Which is very handy, very handy indeed.

(via MeFi, thx Burhanistan)

FURTHER: also from the same MeFi thread, a link for a sumptuous scan of Owen Jones’ The Grammar of Ornament (1856) — which I may have linked before, and I can’t quite be bothered to look right now, but if so, here it is again.

STILL FURTHER: I did, in fact, post a link to a page on The Grammar of Ornament at the University of Virginia Library, three years ago. The page that used to be there has now been moved here, but someone forgot to move the images, which are presently showing up broken. YMMV.