Perhaps a few visual pictures from the Woodworkers Association might help unscramble the wood identification conundrums:

Walnut: http://www.woodworking.org/WC/Woods/161.html
Birch: http://www.woodworking.org/WC/Woods/030.html
Beech: http://www.woodworking.org/WC/Woods/020.html
Maple: http://www.woodworking.org/WC/Woods/125.html

Remember, what the wood looks like in real life depends very much on how it's cut relative to the grain, and how it's been stained.

Hope this helps.