I mentioned that I have been participating in some art postcard swaps on Swap-Bot, and two of the recent cards that were delivered (both from The Netherlands) recently are of artwork by Czech Art Nouveau artist Alphonse Mucha, whose work I love. This particular image is "Laurier", 1901.
The stamp on the back is a "Green" stamp: "think green for a green world".
This image is a detail from one in the series of studies of "The Moon and the Stars" from 1902.
I've gotten quite a few stamps from The Netherlands and I'm surprised at how varied they are. Three more that are new to me. I especially like the stamp on the far right (sorry if it's hard to see details) as it show many more stamps!