Thought AD states there are no nuclear bombs
But that was my point. If you've acquired nuclear power in 1904 why fuss around inventing tanks? Especially since the first ones only came as a perceived means of breaking the trench stalemate on the Western Front.
More advanced artillery, better sights, quick-loading, rapid traverse, longer range, possibly gun shields (but probably in the form of asbestos fascines or gabions), I could see as a natural progression from the book where the only thing that takes out a tripod is artillery (discounting Thunderchild ramming one - going to ancient Greek naval tactics is not progress).
Possibly more advanced communications would be a likely development (a bit boring for the tabletop, but better telephones, portable radio sets etc would be a logical progression) Maybe even a computer. There's a lot of new data to be analysed after the Martian landings of 1899.
Also gas masks/NBC style suits. Historically, anti-gas hoods were developed (by the Canadians?) soon after the first gas attacks in 1915.