The PNG (Portable network graphic) was developed by Macromedia for use in web design, so,.. it can contain metadata.
If you send it as a printed jigsaw puzzle,.. you could print 3DAGE on the bottom corner,... they may never figure it out.
There’s no meta-data on cardboard, or wood,. .... yet.
Adding your customised 3D vehicle to the real world should be as easy as adding a BackDROP, with the real world photo,. and a plane with a shadow catcher shader (for the ground) and then using either lights or an HDRI in the BackGROUND, or a mix or both to create the scene light and ground shadows,.. Using an HDRI will also be used in the reflections on the vehicle.
One more thing,.. In carrara, you can also use a “normal” jpeg image in the background,.. rather than an HDRI.
this means that you could use the Real world photo,. in the scene background, and you’ll get some reflections on the bodywork, from that image.
If you have photoshop you can also create a 32bit HDRI image from your photo.