This lively poster by Henri de Toulouse-Lautrec, of Jane Avril, 1899, is from the Rosenwald Collection and is part of the (Washington) National Gallery of Art’s digital open access collection. The avialability to the public of this collection is great news as there are not many picture libraries of “real” artworks by big names. So if you want to include a landscape or an illustration within a piece of design you can now do so without it breaking the bank. Just check that any image that you use is part fo the open access collection. You can locate these works at this link: https://images.nga.gov/en/page/show_home_page.html
Below is an early and uncharacteristic illustration for Tannhäuser, by Aubery Beardsley again from the Rosenwald Collection. Have fun searching NGA Images!