Wood often provides more contrast than glass does, as you can control how dark the lasering comes out on wood. The darkness of lasered wood is determined by the amount of oils left in the wood. Some woods start out with more oils than other woods. The longer the wood sits after it is cut, the more the oils dry out.
You can color-fill wood with paint, inks, or other fills. How you fill wood may be based on if the wood is finished or not, and how well it is finished. Finished wood can be quickly filled with black or brown shoe polish. Paste or liquid work well. I prefer paste and use a soft toothbrush to apply it, using a paper towel to wipe off the excess. I have also used a product called Lazer Dark, which is a spray. I always mask the wood before lasering, which adds a step. It covers well and is consistent.
Dark woods needing contrast require a light fill such as silver or white paint. Gold can work as well but should be a lighter shade of gold or copper. Bronze and brass colors are often too dark to provide enough contrast on dark backgrounds.
You can also use the same tricks that you use for glass to highlight and add contrast to specific words or graphics.