I was curious about the usage of sets in this contest so I pulled together the data from the submissions (I counted only 28 sets, I believe one was removed after submission which would explain why the previous count was 29).
Here's the data. Unique usage is how many maps used that set (so if a map uses two of the same set that only counts for 1). Total usage is the amount of that set used (a map that uses two of the same set counts for 2 in this case).
Besides the Marvel set of course, the most used set was a tie between Jungle and Forest, each with 8 unique usages and 9 total usages. Right behind them and number 1 among Master Sets was BftU with 8 total and unique usages.
The least used set was Volcarren Wasteland with only 4 unique and total usages.
The most used terrain combination was a tie between 2x Marvel 1x BftU 1x RttFF and 2x Marvel 1x BftU 1x TJ.
Just thought this was some interesting info!