I want to help so here are some links to websites that show pictures of Japanese Castles
http://www.hungry.com/~jamie/castle.html
http://www.geocities.com/castlejapan/
http://www.castlejapan.com/
http://www.obershawonline.com/castle/
http://www.planetquake.com/3/levels/q3a/japanctf/# - this one has pictures of a quake 3 japanese style level (it looks really good)
http://www.jgc.co.jp/waza/a5_himeji/castle01.htm - this one is also very good, it even shows one with a town surrounding it, very detailed
http://www.shirofan.com/english.html - this one seems to be a very good site however none of the graphics are showing up for me
but it does have a VERY GOOD PICTURE of a japanese helmet of some sort (maybe someone can make one for G2K1)
If this isn't enough I can post more, just let me know