Screenshots for BGE
This page probably will not be available until 2015.
For now, you can see a number of screenshots by following the links to the free digital game conversions on the Downloads page, and the links to the commercial Game Boxes on the Store page. Said screenshots were taken in BRPG, so there may be some terminology differences, but the games shown will look the same in BGE.
You can also see a lot of screenshots in the BGE User Manual, which you can download from here.