Antonyms of classy:
unstylish, styleless, cheesy, coarse, crude, flamboyant, flashy, garish, gaudy, glitzy, grotesque, loud, raffish, splashy, tacky, tawdry, ticky-tacky, rough-edged, rough-hewn, rude, trashy, uncouth, uncultivated, uncultured, unpolished, unrefined, vulgar, dowdy, graceless, inelegant, tasteless, unfashionable, unhandsome.
Examples of usage:
  1. But it is some classy order, all right, if you come to think of it; I guess I won't commence to- day.
    "From the Car Behind", Eleanor M. Ingram.
  2. Tom Hartshorne- no one who ever spoke two words with him could call him anything else but " Tom"- was the only exception to this rule; the others were all men of a class, " classy," without any distinctive individuality.
    "Caught in a Trap", John C. Hutcheson.
  3. They were exceedingly " classy"; they affected to regard all the Society of the city with scorn, and had their own all- the- year- round diversions- an open- air horse show in summer, and in the fall fox- hunting in fancy uniforms.
    "The Metropolis", Upton Sinclair.