[Kameron8]

All instances of Ice Sheet creation I can find outside of Elemental Impacts:

• Miu
  
• Famiuga
  
• Ice Arrows + Archer abilities
  
• Ice Trap
  
• Libegrande
  
• Celsius Shell (overcharged)
  
• Crawling Spikes
  
• Expanding Ice
  
• Icicle Spear
  
• Create Ice Point
  
• Frigid Arrow (On a Rain Trap)
  
• Chilling Rune
  
• Kraken's Sigh Triggered Ability
  
• Toyatori
  
• Sogensara's ability, Everblue
  
• Yukijin's on-kill Hidden Cut Weapon Potential
  
• Snow Crow's passive ability, Snowfall
  
• Haku's ability, Ice Jet
  

There's likely a few instances of monster abilities that generate Ice Sheets, and Mercenaries could cause some weirdness because of it, but I don't know those ones off the top of my head.