So I came up with 6 ghost types, (a lot of words I hope thats okay) 4 are tameable using glow berries, one would prefer sweet berries.
#Ghost Content Ideas (upvote my last msg instead if you like it)
tulip surge
Red
Screeches/jumpscares enemy mobs within a 5block distance, doing a bit of damage and stunning the enemy for 2 seconds (rare, aggressive to player before tamed, inside mansion prisons/prison outposts)
Orange
Personal floating storage, ride on the back of your head and if holding food, feeds you itself so you dont have to (taiga, common)
Yellow
Answers the door in the haunted house, you give it candy and he lets you in and every other ghost inside is friendly. if you are rude, he screams and every ghost inside comes out and attacks you (not tameable, but trust can be earned/can trade with? Same size as the plant ghosts)
Green
Glows when it finds the same ore given (Wears a chipped iron helmet. Found by popping out of broken blocks in mineshafts?)
Purple
Shy, wear blanket over self to get close to it and earn its trust (like a enderman and carved pumpkin) turns you invis when you get to a certain threshold of hp, hiding you from mobs(makes gasp/shrieking when casting). (Found in swamp, semi-rare)
Grey (Hostile)
All ghosts turn hostile when player hurts yellow/walks in house without giving yellow candy?
Pink
Regeneration potion effect (same numbers) (Rarest, found in cherry blossom, tamed using sweet berries)
Visuals -
When Green is given a raw ore/ingot, it will find it in the mines within 20blocks of you. It stars glowing and spinning/echoing for you to come mine it. (lasts 10 seconds)
When wearing a blanket, purple ghosts aren't scared/think you're one of them. Allowing you to get close enough to tame them and help them realize you're not a threat. (works like pumpking and endermen)
Red's shriek/jumpscare can look something like this
Pink's healing can visually be portrayed like this at all times/only when you're low
Other content-
Stuff such as hats, globally all ghosts can wear whichever hat the player wants to give them.
The candy that can be given/traded to yellow at the mansion
An idea of the blanket you put over yourself so you can try to tame purple
and obviously the haunted house, which can be a new structure for the mod. (I haven't built one
)
Thats all! The name colors are just placeholders, they don’t actually need to be different colors, these are just ideas. They can all either be shaped the same or shaped differently (longer, wider, etc.). I hope you guys like the ideas, I hope this format was okay to read and understand💔 
Oh I forgot to add, this would be an easier indicator for when your ghost is low on hp or when they are sitting
wait i just realized i deleted the post/you guys cant upvote it
oops
Ghost Content Ideas (upvote my last msg instead if you like it)