Two new movies take a kinky view of fashion trends. ''Tattoo'' is about a demented ''body artist'' who kidnaps a model and inks a mural on her skin. Bruce Dern plays the villain with bewildering intensity, as if this were a real psychological study and not the limp melodrama it is. ''So Fine'' marks the directorial debut of comedy writer Andrew Bergman, featuring Ryan O'Neal as an English teacher who saves his father's garment business by inventing see-through bluejeans. Some fine comic bits are swamped by the raucous tone of the film as a whole, which - like ''Tattoo'' and so many others - condescends to its audience every step of the way.