Fear and Loathing would be horrible for me on psychs. There's just too many negative emotions and actions (the knife scenes in particular) for me to feel comfortable watching it, though I have no doubt it'd be trippy as hell. But if one were to watch it, the intention would likely be to bring about uncomfortable feelings and confront them. Again, not my cup of tea.
I recommend:
Fantasia 2000
Alice in Wonderland
Yellow Submarine
Pink Floyd, Live in Pompeii (kinda dark and spooky, but definitely trippy... "Careful w/ that Axe Eugene" in particular)
...and any Pixar film