A,
First the easy answer - they are 15 mm (or as close as I could get with non-hobby sources or allied like HAT plastic Jungle set for some animals).
Now, how do I use them? Well, I've only recently finished them so they haven't been in a game yet but how I intend to use them is as a visual improvement but also as a "hazard" for armed forces or "civilians" - I like my games to be "in the world" rather than isolated battles. They will also be the focus of a couple of other games - a hunting safari game for a more mature audience or as "targets" of a photo safari game for a more youthful audience, mom friendly games if you will.
And then there's this, I just get a kick out of having them - even if it means I'm put down as one of the hobbies eccentrics. Hope that answers your question to your satisfaction.
G.