Westerfield's divergent World War I where the Entente Powers are Darwinists (utlizing “fabricated” animals as technology) and the Triple Alliance are Clankers utilizing mechanical technology far advanced of our real history, provided a lot of vehicles and devices for Thompson to illustrate. Here's a German war walker in cutaway Osprey books style:
And here's the British leviathan airship where the heroes spend much of the series:
It also has pictures of uniforms of the major armed forces involved:
It's a great companion if you dug the series and interesting even if you haven't read them books. The only faults I can find with it is that it is only a slim 64 pages long and it's a portable 7x9 instead of something in more of an artbook 10x12 range.