Question
I'm building a rather large patio with a lattice grid of 6"x6" pavers. I want to fill the 4'x4' square spaces between the pavers with crushed oyster shells (no, it won't be a bocce ball court). Concrete is way too permanent and boring for this location. Would oyster shells be a good choice? Clay perhaps? I have excellent drainage and low use.

Answer
Oyster shells are a creative re-use.  Some areas have put restrictions on their use (North Carolina).  If you are in the west/midwest, it may be tough to get a few yards of crushed oyster shells.  They are used extensively in Williamsburg, VA for pathways and road surfaces.  

When you put them down initially, they can give off a rather strong odor until they've had a chance to weather.

Another interesting ground "filler" is recycled &/or colored glass. Here is a cool source: http://www.nmmastergardeners.org/glass_page.htm

There are other suppliers that may be closer to your area - I just wanted to show some pictures of the material.

I would not suggest clay, as it doesn't drain well & gets "gummy" & can stain clothes when it does get saturated.  Thats why the "boys of summer" call games due to rainy weather.  We use a lot of bark products & crushed or decomposed granite in the west.  

I have seen other more uncommon materials like slag from mining and steel manufacturing, colored rubber, and recycled & ground up rubber from old tires.  (A quick google search can yield pictures of these in action) ~Marc