Every time a show goes into someone's mind, it's depressingly mundane. Olivia's mind is a city, or her home town. Lwaxana Troi's mind is the Enterprise standing sets
. Even Inception just used real-world locations with maybe some odd shit going on.
It should be absolutely out of control in there!
The film 80s Dreamscape got it much righter. The dreams were downright hallucinatory. The Cell also did it pretty well.