My preferences of postcards are ...
. LANDSCAPES
. famous ARCHITECTURE - castles, TV towers
. snow - winter views
. fantasy - dragons, unicorns
. polar animals
. panda
. whales
. tigers
. trees
. cacti
. cute illustration - Moomin, Krtek, Jetoy
. sailing ships
. trains
. MT. FUJI (Japan)
. Symbolist paintings (like those by Ivan Bilibin)
. Romantic lanscape paintings (like those by Ivan Aivazovsky)
. illustrations by KAORI WAKAMATSU