There are a total of 50 Concepts to collect.
All of the Concepts can be found in the Übercommander Missions (the videos were recorded in those missions). I recommend grabbing all collectibles after beating the main story and unlocking all of the Contraptions.
Some Concepts are only accessible during the Übercommander Missions and are labeled appropriately below.Manhattan - 10 Concepts
Roswell - 7 Concepts
Mesquite, TX - 1 Concept
New Orleans - 10 Concepts
Venus - 7 Concepts
Evas Hammer - 12 Concepts
Riverside - 3 Concepts
(This area is unlocked after completing all 15 of the Übercommander Missions)