I've just received my 'Venus Sourcebook' from the new Space-1889 KS project. If I'm honest, I'm likely to stick with the old GDW stuff, so - if this and any of the new stuff could be of use to anyone, I'd be happy to discuss some ideas, e.g., trade/swap options.
Those are great 15mm figures and would certainly be perfect for Venus/Space-1889. As mentioned already by others, climate/environment plays the major role, so loose-powder firearms are worthless. Means sealed metallic cartridge firearms - so Boxer cartridges for Martini-Henry rifles for example - become very important. From most of the fan-made Venusian stuff I've seen, the loyal Venus troops assisting the human powers still tend to resort to their own weapons. Quite sensible I guess. But there should be some provision for ultra-loyal types - I'm thinking a Ghurka-equivalent lizard tribe for the British, perhaps a tribe that mimics East African/Tanzanian Askari-types for the Germans - and give these lizardkin some firearms?
On another tack for VSF, these 15mm lizards would also make a good opposition force for some sort of Atlantis/Lost Civilization theme - typical mass hordes encountered while Journeying to the Centre of the Earth? (Then just need a 15mm Doug McClure?)