Short Summery of Slippy Surfaces (SSoSS):
Frozen grass - most consistent as long as you avoid heads of clumped grass. However, the resistance from the frozen blades eventually wear you out a little.
Frozen gravel - Walked this the most, either in the middle of the road (no one's driving in this crazy weather) were the road is balanced or I walked the very edge were there is a slight incline but the roadside grass prevents my left foot from too much slippage.
Frozen cornfields - Not very user friendly. The turned over soil made it even worse, they were like big slippery jagged rocks. So you move... very... slooowwww.
Frozen rocks & pebbles - Slippery and dangerous and not worth it and crazy town.
Frozen paved roads - Straight ice rink without the zamboni. But, if hail has previously fallen earlier or day before it provides okay traction.
Frozen ditches - These weren't too bad as long as they weren't filled water or long strands of grass.
Frozen mud - Not bad and sort fun to walk on. With a layer of dirty ice on top and melted ice water in between it almost like walking on rough plexiglass. It's also cool watching the air bubbles dance beneath the ice.
I walked on white snow or ice whenever I saw it. It gives excellent traction to prevent you from falling. If it wasn't bright white, it is suspect in my book. Especially at night, you can't miss seeing it even with little light around.
If you are unsure about a surface while walking in icy conditions take my advice and just walk like a elderly person, meaning take your time! It may not look cool, but it will prevent you from becoming a falling fool.