KATHE BURKHART, Serge Sorokko Gallery, 430 West Broadway, near Prince Street, (212) 941-8888 (through Dec. 1). This show offers a sampling from the ''Liz Taylor Series,'' which this artist has been producing for the last decade or so, and suffice it to say these paintings make Warhol's ''Liz'' look like the last word in self-effacing decorum. Ms. Burkhart's big, brash film-clip-style images are enhanced by a variety of applied textures and unprintable expletives. It's all too much, which is exactly what it's supposed to be (Cotter).