Suggestions - oh dear. You realise that opening the "can you give me ideas" can of worms means thousands of posts of disagreement, flaming and dissent! One constant is that players never agree on house-rules... especially if they have played and lost against them.
Anyhow:
Psychic Powers:
Horror
All non-cult models within X" (12" maybe) must immediately pass a Ld test. If they fail then they must fall back 2d6" towards the nearest table edge/cover to cower in fear.
OR
All cult models within X" cause Fear / Terror for one turn. (normal upgrades to cause Fear, those that cause Fear now cause Terror)
Catalyst
All cult models within X" gain Frenzy for one turn and may move an extra D6".
OR
All cult models within X" gain +1 MA, +1 WS, +1A for 1 turn.
Psychic Scream
All non-cult Wyrds within X" must immediately roll on the Perils of the Warp table as if they failed a psychic test.
OR
All non-cult models within X" are pushed back / fall back X".
OR
All non-cult models within X" suffer a S7 hit but use their Ld instead of their T when rolling to wound.
Psychic Blast
Target a single model within X". Model must pass a Ld test or automatically be "downed".
OR
Target a single model within X". Model suffers a hit with strength equal to the attackers Ld.
Metamorphosis
Target cult member within X" rolls immediately on the mutation table.
For the Hive!
Target cult member within X" explodes! Gas cloud template S4 hits. All non-cult models in area must also pass Ld test or fall back.
Adrenal Surge
Cult model targeted may act again this turn. After acting suffers a S3 hit.
Unnatural Regeneration
Target cult member regains 1Wd.
Mindslave
Target model must pass Ld test. If failed then Cult player may make them take one immediate action (not suicidal!)