Ice Queen: any kid mohair, but I say go for the kid silk haze, it's only 1 ball!
Aran, Worsted & DK Yarns
Aspen Cowl: i've already made this one, it's a welcome part of my winter wardrobe in deep winter. sub Misti Baby Alpaca Worsted, Suri & Silk, Manos Silk & Wool.
Dark Side Cowl (Ravelry): sub Manos Silk, Jo Sharp Silk Road Aran Tweed or Cascade 220 Heathers.
Limulidae Cowl (and hat!): sub 2 strands of Nashua Brushed Alpaca held together, Misti Baby Alpaca Chunky, Cascade Eco, evem Lamb's Pride Bulky.
Cherry Garcia Cabled Cowl: sub Lamb's Pride Bulky, Misti Alpaca Chunky.
Sophia Knits Cowl (on ravelry): sub brown sheep Burly Spun or Estelle Woolly Bully, only 1 skein of either.
Envy Cowl: i really like the cable up the sides! no need to sub this one.