There have been a few custom bolt guns built with marquetry and it is common on older Weatherby rifles in simple diamond forms.
I've wondered about doing the same thing.
I think it's a fine idea for a modern rifle, just be subtle and conservative. Some of these guns are about historical accuracy, some are about art and history, and I don't see why some can't be all about art with no pretense of historical accuracy.
If the inlay is darker than the basic stock it might not give the "gaudy" impression that light colored wood will, but the contrast will be sacrificed.