René Vincent was a French illustrator, painter and poster designer. Prevalent in the 1920s-1930s, he worked in the popular Art Deco style. His illustrations helped define early 20th-century advertising, birthing countless imitators and admirers alike. Tintin creator, Hergé, cited René Vincent as an inspiration.
Almost two decades before Norman Rockwell, J.C. Leyendecker was synonymous with The Saturday Evening Post, producing over 300 cover illustrations for the magazine. I love his super stylish and super cool male protagonist he paints, and the way his work invites you in. There is a nice collection of his work here and here, but for a truly amazing collection check out this J.C. Leyendecker book.