Actually, as ridiculous as it sounds, this has happened to me many years ago with lorazepam. I took several before watching American Beauty, and I was put in to a very strange place of time distortion and other weirdness. It is kind of the same type of experience that zopiclone or zolpidem can produce, and it only happens the first time you take them after not having used a benzo for a long while. The experience to me is characterized by a very dreamlike, almost delerious state, where you get lost inside your own mind whilst still being wide awake and sensing things. I wouldn't characterize this as "psychedelic" in the classical 5-HT sense. Hallucinatory, yes.
I once took some zolpidem and I was seeing lesbians come out of the wall. Another time with it there were rotating smiley faces made of pure light spinning on the ceiling and beckoning me to join them. Yet another time I was having a conversation with my rubber plant, which was moving it's leaves and transmitting it's thought to me telepathically. I've seen ethereal beings made of rainbows and light walking up and down my room before whilst I've been "tripping" on zolpidem. Zopiclone is similar, but more hypnagogic. Again, you cannot get this to work two nights in a row, or if you have taken benzodiazepines in the past few weeks or months. It's also not reliable, as in you cannot expect that you will definitely trip if you take x amount.
I've also personally witnessed other people on zolpidem clearly hallucinating. I was with a couple of friends once, one of which took a large dose of zolpidem, and he turned in to a complete wreck. He was talking to the speakers, having conversations with people who weren't there. We had to carry him downstairs, and help him over the garden wall to take a piss in the alley, in which he shit himself!
I also have had some strange experiences with diazepam. A couple of times, when I took it after not having used it for ages, I would actually get CEVs of blobs of colour. Nothing spectacular of course in comparison to 5-HT psychedelics, but for a benzo it's pretty amazing. The most intense experience was when I combined diazepam with promethazine (can't remember the dose) and I was entranced by a colourful lightshow behind my eyelids until I fell asleep.