Has anyone seen the the Obakemono Project: http://obakemono.com/introduction.php There are a good many monsters on there that would certaintly spice up any oriental themed campaign.
I don't know if you're formiliar with the WotC' D&D Oriental Adventures. But a number of the monsters/demons listed at Obakemono can be found in it. It should be possible to use those as a baseline to convert all....