I have been riding the fat bike a lot, and part of why it is so much fun to ride is because I don’t have to where spds. Yup I ride in Sorels, and the pedals I have been using are 45Nrth Heiruspecs.
They are a lightweight alloy pedal with nubs not spikes to keep your foot secure. I say not spikes because they are not sharp shin splitters, just enough to keep your shoe on. The spikes are actually removable and you can change the color.
So if you need flat pedals for your bike, check these out.
45Nrth says: http://45nrth.com/products/category/pedals
A wide flat pedal with wicked grip. Supreme contact with the bottom of your traditional winter boots is now possible. The wide CNC-extruded body of the Heiruspecs provides a massive footprint for the big boot of your choice. Sixteen alloy pins spread across the concave body provide the ultimate grip. Replacement pin kits are available separately in different colors so you can color-coordinate your rig.
Ooh, nice looking flats. I use plastic BMX pedals on my fixed commuter and love 'em.