The promo photo with the 1969 Trans Am in the background was from one of the General Motors Annual Reports (I believe), I can't recall which one.
Pontiac used the 1969 Firebird model several times in the promotion of their 1970 wagons. The theme was that the wagon was spacious, built for a family, while the Firebird was not.
Here's a few more:

In this one, the Firebird in the background shows a woman pushed forward in the drivers seat, trying let someone out of the back seat. The message here is that the Firebird is cramped, the wagon in the foreground is not.

The family is leaving, all packed into their new 1970 Bonneville wagon, while the 1969 Firebird is relegated to the garage.

This photo shows a couple trying to cram a plant into the trunk of their 1969 Firebird, while spacious 1970 LeMans wagon in the foreground seems a lot more practical.

Here's a 1969 Firebird 400 with what appears to be a 4x8 panel strapped to the roof, while in the foreground is a spacious, more practical 1970 LeMans wagon.

Finally, if you want to go skiing, the 1970 Bonneville wagon was far more practical than the poor 1969 Firebird in the background.
Mike
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My Bio: I am currently writing articles for POCI's Smoke Signals magazine and enjoy promoting and discussing the history of the Pontiac Motor Division.