It was an auction for 7 game music posters that happened to be listed in the game music category on YJA. The other 6 were for individual albums, which I added to their respective pages. They were:
Super Mario Bros 3 G.S.M. Nintendo 1
Galaxy Force G.S.M. Sega 1
The Ninja Warriors G.S.M. Taito 1
Syvalion G.S.M. Taito 3
Game Sound SNK G.S.M. SNK 1
Konami Game Music Vol. 4
As for game posters, you can use this search for arcade posters:
http://category.auctions.yahoo.co.jp...p=ポスター
As a guide, B1 size posters are 1030 mm x 730 mm, and B2 posters are 730 mm x 515 mm.