Basic knowledge of painting: http://webneel.com/types-of-paintings-techniques-styles https://blog.orangecarton.com/an-introduction-to-different-types-of-painting-styles/
Styles: Abstract Art, Landscape Painting, Still Life Painting, Contemporary art, Concept Art, Photorealism, Hyperrealism, Surrealism, Modernism, Impressionism, Expressionism, Pop out Paintings, Figure painting, Body painting, Mural Painting, Street Art, Chinese Painting, Japanese Painting, Korean Painting, Islamic Painting, Indian Painting, African Painting and Veduta.
zip files: from: http://www.smk.dk/en/use-of-images-and-text/free-download-of-artworks/ download links: http://foto.smk.dk/Dansk_og_nordisk_kunst_1860-1910.zip http://foto.smk.dk/Dansk_og_nordisk_kunst_1750-1859.zip http://foto.smk.dk/Europaeisk_kunst.zip http://foto.smk.dk/Grafik_og_tegnekunst.zip
web pages: highly recommended: https://www.wikiart.org/en/paintings-by-style http://www.classicartpaintings.com/
other pages: https://www.nga.gov/ http://www.comuseum.com/painting/ http://www.comuseum.com/painting/famous-chinese-paintings/ https://artsandculture.google.com/search/asset/?p=the-national-museum-of-western-art&em=m031cgw&categoryid=medium https://artsandculture.google.com/partner/the-national-museum-of-western-art https://images.nga.gov/?service=category&action=show_content_page&language=en&category=16 https://theme.npm.edu.tw/opendata/DigitImageSets.aspx?lang=2&Key=^^03000117 https://www.allartclassic.com/paint.php?alphabet=A http://collections.vam.ac.uk/search/?listing_type=&offset=0&limit=15&narrow=&q=Indian+Company+Paintings&commit=Search&quality=0&objectnamesearch=&placesearch=&after=&after-adbc=AD&before=&before-adbc=AD&namesearch=&materialsearch=&mnsearch=&locationsearch= http://www.mfa.org/collections/asia/tour/japanese-paintings http://www.mfa.org/collections/asia/tour/chinese-master-paintings
reddit: https://www.reddit.com/r/painting/ https://www.reddit.com/r/drawing/ https://www.reddit.com/r/Watercolor/ https://www.reddit.com/r/sketchpad/