Three small pieces off my sketchbook in the past few days, as well as some commentary.
1. (WIP) Full Color Fed

Work-in-progress piece. This States-Grenadier will go into the Federal painting guide appendix: thus, when he's done, he'll be fully colored. I may try my hand at some rendering with him. The other factions will each receive an example full-color infantryman in their painting guides too.
Something that may bug the more technically minded members of my audience is the absence of shoulder straps to help bear the load of his ammunition and other belt gear. For a while I simply went without it: soldiers in the American Civil War, one of the main Federal aesthetic inspirations, wore belt gear without any suspender system. But the increased weight of the entire combat load (forty rounds versus a hundred-fifty or more, plus the rest of his gear) somewhat stretches the believability of that.
One solution, from real life, is internal suspenders. Early WW2 German jackets featured such a system, with holes for hooks that would carry your belt and suspenders:


These were, in real life, supplanted or replaced by external suspenders (the classic leather Y-straps practically every European military used). They were an inferior choice from a production and complexity perspective. But they did look good, and one of the reasons I draw fantasy troops is because they look cool. Probably the lack of 20th-century style total war in Firelock--waged to industrial and populational exhaustion--contributes to things like these hanging around.

This Federal NCO sports some protruding belt hooks, not hidden by any worn belt gear. Probably a variety of slightly different such systems exist across the States-Army. His funny round hat is based on the M1839 "wheel" cap, the Mexican-American War-era predecessor to the Civil War kepi you've seen on grenadiers before. Where the kepi is equivalent to a patrol cap, being a practical piece of headgear worn at the front, the wheel cap is for garrison use: it's a pogue crown.
2. Territorial
A clan militiaman getting his rounds in on some deep-woods rifle range. His hat and pants are a simplification of the White Gloves' dress uniform: the premise being that these are some ancient uniform items belonging to a family member that fought in the AEF a long time ago. The Gloves' uniform is essentially a more decorated version of the utalitarian sets worn by the troops of the Regency when it was first established: something 1890s in feel, the last generation of non-camouflaged uniforms.
This is a piece I'm not very satisfied with myself. Even if a shooter's bench doesn't produce the most dynamic poses, there are still better ones I could have gone with (e.g. supported shooting) than this neutral standing position.
3. Pigboat
A Federal submarine and a tube-launched cruise missile. While naval assets are not applicable to the tabletop game, they're still a lot of fun to think about (and something that, in the distant future, I'd like to explore in greater detail).
The boat itself is based mostly on the various Soviet diesel-electrics of the Cold War: Whiskeys, Tangos, Foxtrots, Zulus and more. They all generally had rectangular profiles with squared-off knife bows reminiscent of the Type XXI from WW2. I imagine that since the Federal States-Navy is the largest such force on Oid they would maintain a great many of these cheap, reliable diesel boats for patrol and escort duties.
The conning tower is based on the US S-class submarines: late WW1 dinosaurs. This is a matter of personal affection. I've wasted countless hours of my life commanding S-boats against Japanese shipping in Silent Hunter 4, and I have a special place in my heart for those scrappy, rusty, leaky little "pigboats" and their crews.
Added to that mix is a stern deck gun mount. The deck gun is worse than useless in modern submarine warfare: surfacing is a great way of being hit with a dozen missiles from several dozen kilometers. But since war in Firelock is not total, there are plenty of little escapades and adventures a submarine could get up to--shore insertions or bombardments, special transport, or privateer cruises--where a simple, well-stocked, short-range weapon would come in handy.
Compare and contrast to the light guns that pretty much every modern warship still carries: they don't seriously expect to use these against anything bigger than a suicide speedboat or the like, but they may still situationally be useful.
The missile is essentially a turboprop Tomahawk with unfolding propellers. This is ridiculous and exists mostly because I think it's funny. It might be too flanderized in retrospect--Federals can produce jet engines (a turboprop being a turbojet with extra steps, after all), but they don't make jet fighters for doctrinal and stubbornness reasons. These wouldn't apply to a cruise missile.