What's with all of the spirals?
The first paintings Jon shows Dany appear look like swirls and spirals, some of them perhaps cosmic in origin, but others – as creator David Benioff explained after the episode – are meant to evoke the patterns the White Walkers arrange their victims in. We see an example of this in the first few minutes of the very first episode, when the Nights Watch rangers happen upon dismembered Wildling bodies arranged in a circle.
Benioff explained that the patterns didn't originate with the Walkers, but with their creators: "These are patterns that have mystical significance for the children of the forest. We're not sure exactly what they signify, but spiral patterns are important in a lot of different cultures in our world, and it makes sense that they would be in this world as well."
In our world, the Fibonacci sequence, a series of numbers that approximate a logarithmic spiral, appears constantly and unexpectedly in nature, like in sunflower heads, the sprouts of a pineapple, and in pine cone bracts. Many ancient civilizations -- from the Mayans to the Celts -- depicted spirals in their primitive art. Galaxies, hurricanes, seashells, fingerprints; spirals are coded into our universe.
It's hard to say if spirals will ever mean anything specific or significant in what's left of Game of Thrones, or if they're only meant to draw a connection between our physical world and that of Westeros. But that Benioff chose to emphasize their significance means we'll probably, at the very least, see some more elaborate White Walker body art by the time the show is over – full Fibonacci style.