Wonderwall is fun, but don't go into it expecting much of a plot and personally I don't think of it as a sex flick, although it does have some mild titillation in there. Worth it for the heady 60s atmosphere, if you can take Jack MacGowran in buffoon mode. I suspect you'd be better off with the shortened director's cut.
For something (superficially) grittier, how about Zachariah? An "Electric Western" featuring performances from Elvin Jones, Country Joe and the Fish, Doug Kershaw, and the New York Rock Ensemble, it was written by the Firesign Theatre, although it doesn't contain much of the depth or humor of their albums of the time (1971). We've hit the 70s and are in the "old west" so it's not as light and trippy as the previously mentioned films, but it's plenty weird in its way, and features more gay subtext than you can shake a stick at (if that's your idea of a good time). With Don Johnson, very popular with gay male audiences at the time, and Dick Van Patten.