Others can be used with diminished fifth T-5b-O.If u add a 7th or minor third, it's not really a power chord anymore, neither a dimished chord( which is T-3m-5b-7b).
Sus 4( T-4-5) or 7/sus4(T-4-5-7m) are aslo commonly used in (Hard)Rock.
U can aslo try these type of chords which sounds quite nice: T-5-9.
Darkangel