I subscribe to Dover's Free Sampler, which often has fun printables like coloring pages, paper dolls, etc. I especially love the artwork coloring pages they sometimes share. These coloring pages based on famous works of art and artistic styles would be great to help expose kids to artists from various periods. I like the idea of letting kids color the picture first without seeing the original, then see how theirs differs, and what difference that makes in how the artwork looks.
Dover doesn't keep these up indefinitely, so you may want to download these for later use. (A few of these are not from Dover, but most are)
Spot the Difference Artwork (Van Gogh and Mona Lisa)
Van Gogh Paintings
Impressionist Art Stained Glass (includes work by Degas and Van Gogh)
Impressionist Art (Degas, Renoir)
Renoir, Various Works,
Degas, Dancers
Art Nouveau Stained Glass
Various Still Life Coloring Pages (including Cezanne and Riviera)
Cezanne, Various Works, Artwork 2
American Painters (including Benjamin West and Thomas Hart Benton)
Mona Lisa
Monet, Resource 2, 3, 4 (various paintings)
Raphael (The Sistine Madonna)
Mexican Folk Art
How to Draw Mandelas
More Fine Art Coloring Pages on Education.com
Abstract Art
Golden Age Illustrators (Famous Fairy Tale Illustrations)
Art Appreciation Mempory Puzzles
More Artistic Coloring Pages Here (it may show this post first, but will also show all my other similar posts if you scroll down)