Of all of the toy companies out there, LEGO is very guarded with their design concepts.  Every once in a while a few appear on the Interwebz, and I recently pulled a few off of /toy during one of my fits of insomnia.

Included in this gallery are mock ups of what would become Space Police II and Aqua Raiders.  The others are themes that never came to be, like the updates to Blaktron, a Colonial Village and the Seaquest DSV-like SeaTron.