The Dalek design is quite stylised, so that it works as a purely geometric design too. I'm looking forward to wearing it out and about and seeing who spots the Daleks. ;)
For the colourwork, I've used stranding (or fairisle) technique for some rounds and mosaic (or slip-stitch) technique for the rest, to avoid having too many long floats on the inside. Using a combination of the the two also makes it a quicker knit than if it were all stranded.
For the stranded rounds, I used my newly-acquired two-handed stranding technique, which I'm getting more and more comfortable with. I made a larger one of these for Willie, with a variegated yarn for the Daleks and a solid colour for the background, which worked really well. I still need to catch him so I can take a photo of it!
The yarn I used is Little Wool Company '8ply Pure Wool Naturals', in the colours 'Papa' and 'Pumice'. It's undyed and subtly heathered, and really softens up after a warm wash. After blocking the finished hat, I can wear it next to my skin perfectly comfortably.
I also have a matching pair of mittens planned... :)