In France, the painting revolution preceded the Art Nouveau. The "impressionists" and the "independent club" clashed with academic and historical art down from the mid seventies (1875-90). At the contrary, in Austria or Germany, the name sezession meant a revolution in all Arts including paintings. The Nabis, headed by Maurice Denis, is a painting movement very close to Art Nouveau. They used stylized shapes and especially women faces and clothes with a Preraphaelit manner, very close to placards or stain glass technics : the perspective is flatten into wide plain surfaces of color wrapped by a black or blue thick line.
In applied arts, the influence of nature as a unique source of inspiration began in the 1880ies with jewels, glass and ceramic work, .... The revolution comes from architecture and applied arts. The two main centers of Art Nouveau in France are Paris (the heart of France) and Nancy but you may find art nouveau architecture in many towns : for instance in resorts towns like Vichy, Mers les bains, Hermanville... or other big towns like Lille, Orléans, ... In fact, you may fing Art Nouveau in any town that was in expension during 1890-1910 because of industry, trading or tourism... and that was not heavily touched by the two world wars.