From the IceHUD wowinterface page:
Frequently Asked Questions
1. How do I hide the default Blizzard player and target unit frames?
Type /icehud, expand the "Module Settings" section, click "Player Health" or "Target Health," and check "Hide Blizzard Frame" (NOTE: before version 1.3.7, the player/target unitframes were hidden by default. Follow the same steps to enable them if desired)