In a wood shop, 12 foot ceiling ain't all that high. In addition to the items mentioned, such as a vertical wood storage rack, the higher walls are also used to store/hang jigs and templates that are not used all that often, but still get used.
Also, somewhere in the rear (depending on the length of your shop) you can drop the ceiling down to 8' by creating a small loft area 4 ' high for long and unusual pieces.
I have had several different shops including a spare bedroom, a 45'X100' warehouse and everything inbetween from 8 ' ceilings to 25' ceilings. All I can say is "the bigger the better". Once you have built the structure, it's too late to change your mind.