The venner is usually an exotic or a fancy grain hardwood over some sort of cheaper core material, in higher end humidors this is more likely made from poplar or a lesser grade of mahogany ie. luan that will not have the grain patterns of the veneer it could also have knots or discolorations , on lower end humidors this core is either mdf (medium density fiberboard) or partical board about the best you good do without reveneering is to paint it. Custom humidors like the ones that geek member Kent builds are made from solid hardwood if you can find one made from solid wood you could refinish it like you are talking about.