You can see some of his works in "The Baum Bugle," the official journal of International Wizard of Oz Club.
According to this site linked above, his works appears on "The Baum Bugle, winter 1996."
(You can buy a copy from IWOC's online shop.
It says "autumn 1996," not "winter 1996." I don't know why.)
Mr. Nakai told me that he has 72 Oz paintings and sent me six of them to display on my blog.
(I can't thank him enough.)
These are the paintings. Click to enlarge.
Words like "marvelous" and "amazing" do not do them justice; These paintings are just fantastic!