Hell yeah, those are great! If you give them grey skin, they could work very well as Dark Irons as well! You could maybe do something through Geoset Animation colouring. Could be nice, especially if you give them all glowing red eyes as well, and maybe introduce some lava motifs throughout their gear.
If I may make a few recommendations:
The Rifleman's gun looks a little weird. The shapes are sort of too amorphous and especially the wrap at the end of it looks a little off. I'd maybe add a metallic animal head to the end of it, 3D modelled - something like the lion from the human ships, the eagle from the siege engine etc. And change the shape a little so it's less like a blob and more like a gun.
All of them have blue eyes. There are other textures in the game, and I'd definitely give them different eye colours to differentiate between the different units better. There are grey, red, green, light blue, pink and brown eyes that I know of. I'd also try and differentiate the faces of the Rifleman and Warrior a little more, by using a different texture (maybe Bandit or Bandit Mage?), and change up the silhouette of their helmets a little. Use different styles for each of the units - this applies to the Knight as well. The Knight could use a winged helmet, for example, or big antlers like on an elk. The Rifleman could use a simple skull cap, undecorated, or perhaps some sort of metal coif.
The Mage's head looks too similar to the Paladin. I'd use a different 3D base and wrap the Paladin's texture on it - anything will do, but I'm thinking one of the in-game dwarves would be suitable. Otherwise, just break up the silhouette a bit - make the nose bigger and wider - forehead more squat - eyes further apart, etc. Anything to make it look a little less familiar to its origin.
I also think the custom texture is largely unnecessary as much of this can be done with in-game textures and vertex colouring, but... One custom texture for all of those models is fine, I suppose.
Is the Mage's staff supposed to be white and untextured? It is that way in your screenshot as well as in "View in 3D". Is it fine in-game or did you mean for it to be like this?