Straight up to 70% for 30 seconds in severe icing conditions. No more. Just a few years ago a well known Brit airline crew in a 737 went to full power at Aberdeen (short runway) held on brakes. They ingested many pieces of tarmac sucked up in the not-insignificant time they had full power before releasing brakes. It damaged the runway, the engine and the tailplane (debris spattered at it). A warning was put out to everybody NOT to do it.
As for PA warnings in severe icing conditions, yes- if you are feeling generous and have time available.