Traditional Experience Korea
When you are inside the transit area of Incheon International Airport (around gates 33-37), there is an interesting counter called "Traditional Experience Korea). If you have enough time to wait for your flight, you can go there and try making some of the Korean art and craft on your own. After making, you can do the painting yourself and can bring it back home as a sorvenir! There is also an area here with some books (with lots of colour photos) on the attractions, history, architecture of Korea where you can sit and do some reading.
This place is good to spend sometime when you are bored while waiting for your flight :)