This is all 25/28mm musings...
I have my plans for the British (Empress Miniatures). And the French (No Manufacturer Yet, but leaning towards Askari). And Germany (Copplestone and Eureka). Even Texas, the Papal States, and the United States have at least some thoughts, if not much in the way of purchases or paint applied.
I have (red) Martians from RAFM and Parroom Station. Lizardmen from GW. Plantmen from Hydra. Parrotmen (Kroot) from GW. All planned out, some purchased and painted.
I have a plan for Automatons of various types and manufacturers (Wyrd, Reaper, Hydra and Parroom Station, so far!), and a mad scientist or two to run things.
But there is more out there!
Turks. Exotic. Unusual. Cool. A steam elephant is made by Stonehouse Miniatures. Warrior Miniatures carries some alternate history WWI Turks that would make neat VSF figures. And Ironclad Miniatures out of the UK make some Martians that would make dandy Turks. Find some cavalry figures (preferably lancers) and mount them on steam horses (Mage Knight makes them) for steam cataphractoi. Tiger Miniatures (available via Recreational Conflict http://www.recreationalconflict.com/ in the US) make some interesting Turks as well, in their Balkan Wars line, though I am told they are a bit smaller.
Russians. I haven't yet looked into which Russians would be good. But I think I want some. Any suggestions?
Japan. Like these guys are gonna get left out in the cold? I like Parroom Station's boys. But what else is there? Need more investigation of these.
Did I leave anyone out?