Twelve Kingdoms autographed reproductions are of the new 2013 novels published by Shinchosha. Each one comes with Akihiro Yamada's autograph and are framed and matted. These are most likely limited edition.
So far there is only 2 different types autographed reproductions:
(十二国記 山田章博 複製原画「月の影 影の海」)
(十二国記 山田章博 複製原画「風の海 迷宮の岸」)
This page is a rough translation in English using a translator app. So any english words are not official--take it with a grain of salt.