This article doesn't speculate on the nature of a hexagonal feature seen in Saturn's clouds at its north pole, but my first guess would be that it is magnetic in origin.

Any other ideas?

There's a lot of material on the net about hexagonal shapes on earth and Mars. Those shapes on earth are huge crystals that form over time in permafrost.

Here's a comprehensive article about formations on earth. Some are quite large. They are sometimes heaved up, as they expand the crystal size, above surrounding territory.

So you're suggesting this is somehow related to crystaline structures in the frozen clouds?

I don't know about temperatures there. Could there be some massive 'cloud' of water (or a water solution) (it might be a cloud in the sense that it 'floats' in a denser substance even if it's solid). Do you know anything about its temperatures at the poles? Probably really really cold!!!