generally, i find "psychedelic" films to have extended boring parts--or at least parts that some people will find boring. lots of experimental films are psychedelic--and experimental films are often incredibly pretentious, sometimes bizarre crap.
bunuel's simon of the desert was brought up--probably my favorite "art" film. 45 minutes, with maybe 5 minutes of anything remotely psychdelic. one of my favorite films, but i'll admit to it having its boring moments.
cremaster cycle was brought up. certainly experimental, i guess it was psychedelic, but god was it boring. maybe half an hour of entertainment in the entire cycle. for some reason, many experimental filmmakers love forcing macabre and unsettling images on the viewing public (from The Andalusian Dog to 120 Days of Sodom). i'll try to concentrate on more enjoyable films than challenging.
if you're looking for more like Fellini's Satyricon, check out Juliet of the Spirits. It is less psychedelic than Satyricon, but it benefits from a Nino Rota score and is an exquisite film. My favorite Fellini.
if you want something really fun and more psychedelic than elton john during that rainbow feathered mask and cape period, watch the sun ra film "Space is the Place." you got sun ra and a black overseer playing a card game for the destiny of mankind, you got NASA g-men trying to get sun ra's interplanetary propulsion device and talking about the black space program ('we'll put a coon on the moon by june'). the sun ra music is a plus or a minus, depending on who you are.
i'd look into "A Boy and His Dog" if you like sci fi flicks. more psychedelic than Mad Max or other post-apocalyptic visions, but not the sheer madness of Holy Mountain or a Fellini film. things head for the bizarre once the boy meets a colony trying to survive below ground. it has one of the best endings--and certainly the best ending of any talking dog movie.
there was an Australian film, Sweetie, that was able to straddle being crazy and still being approachable. Neurotic woman with dendrophobia (well, scared of only one tree, I guess). I can't remember too much of the plot (drama in the family), but certain images have stayed with me for years (tree cracking pavement).