I've seen some of the photos of splicing 2 beams to get the desired thickness, but what about the length? Can one join 2, 16-foot beams at some point, to create a 32' length?
Yes . Generally the joint / connection is done centered over a post.
(http://www.strongtie.com/graphics/categories/AC-post_caps_bases.gif%20)
link:http://www.strongtie.com/products/categories/post_caps_bases.html
Just hover the mouse arrow over the different type post connector / bracket/ hangers and they pop up. On the linked page , that is .
The single beam of course has to be sized properly, could be lumber , LVL, Gluelam , Paralam , etc .