An ice storm is both a beautiful and horrific scene in a garden. The potential for major tree/shrub breakage is staggering. If you feel powerless, this is good thing. During the storm, do nothing / “hands off”. Most actions will likely cause more damage than what nature may have intended.
After the storm assess the landscape areas which seem most vulnerable, or that trouble you most. Next, hire an ISA* certified professional arborist to fit your landscape into his/her schedule. At the time of the storm, arborists are likely much too busy with emergency callers.
First on your list should be large trees not pruned in many years. They are likely shedding diseased, pest ridden, or broken limbs. Weak wooded species like silver maple (Acer saccharinum), sycamore or planetree (Platanus spp.), Bradford pear (Pyrus calleryana), poplars (Populus spp.), and willow (Salix spp.) seek to always drop anything from small twigs to large branches. Large evergreens like white pine (Pinus strobus) and leyland cypress (Cupressocyparis x leylandii) frequently deposit broken branches following stormy weather.
Ironically, the trees suffering the worse damage are those topped by neighbors and utility companies. The re-growths are very weak and snap off when the ice load reaches critical mass. Properly pruned trees ride out most ice storms. Take care of your trees and trees take care of you.
*International Society of Arboriculture