This information was taught to me by Kuzuhara Hiroyuki a Toko no Ma and Seki Kazari Sensei who works to teach others the art of displaying in a traditional Japanese alcove, called a Toko no Ma. Here I have broken down the small figurines or accent pieces that are used to explain the story in the display.
In his books I have only studied a little bit about the 添配accent pieces. But the first point that he hammered into me is to understand how to rank the various pieces from most formal (真 Shin) to Semi-formal (行 Gyou) to informal (草 Sou). The ranking is based upon primarily by what the image depicts and the second is with what the material the piece is made.
Formal (真 Shin) Divine Images Buddha/ Temples, Pagodas,
Shinto Gods etc. Jinja (Shrines) etc.
Semi-formal (行 Gyou) Buddhist Priests, Masterless Towers, Bridges, Rookeries
Samurai, Wise men, Nobility
Informal (草 Sou) Travelers, Woodcutters, Fishermen, Grass thatched roof House,
Other Informal (草 Sou): Boats, Rafts, Calligraphy/Paper Items, Animals, Bugs, Fruit etc.
The following are ranked as formal pieces:
銅製 どうせい Copper/Bronze
銀製 ぎんせい Silver
真鍮 しんちゅう Brass
石 いし Rock
The Semi-formal Pieces are:
陶製 とうせい Ceramics/ Earthenware
The Informal Pieces are:
木彫 もくちょう Wood Craft
牙彫 げちょう Ivory/Teeth Items
竹根彫 ちくねちょう Bamboo Made Items