After a few months of trial and error, I think I finally figured out how to do these "miniature" or "tilt-shift" images right. My earlier attempts with the St. Louis images were too blurry. And I was using the wrong kind of blur. I also figured out the best set of color and light adjustments to make them look like models or toys. Here's the corrected STL set.
St. Louis Toy Town
The Old Cathedral
Bush Stadium (or is it now InBev Stadium)
STL Front & Center