There was a series of Wood magazines from a year or two ago that showed
how to redo a complete rom in an Arts & Crafts style. I remember that
they specifically showed how to make air grilles, but I don't exactly
recall how they did it. You might research this to see if you can get a
hold of the back issues.

Joe in Denver
my woodworking shop:
www.the-wildings.com/shop/