Does it feel like all the units are the same regardless of what faction you play? That's cause they are! Brad has stated one of the primary goals right now is faction differentiation. Here's one idea that might help and make the game more interesting.

Custom weapons/traits for each faction.

This seems so simple and obvious to me that I really don't know why it hasn't been implemented. The key is to make them fit with the flavor of each race. Here's some easy examples.

For Yithril - Greatclub - A massive stone club so heavy that only a Trog could think of trying to wield it. It is a two handed weapon that has high attack power and gives the unit bash (like orges can knock units prone). It is very heavy though and will nearly max out the encumberance of even a trog meaning they cannot wear heavy armor.

For Tarth - Bolas - THis would be an accessory like a throwing knife. A weapon once used for sport in the gladiator ring. The tarth have embraced and  perfected it and enjoy watching heavily armored opponents stumbling around on the battle field. This would give them a bola throw ability. I was thinking 3 range. Lowers initiative for that unit for the next 2 turns and has a chance of knocking the unit prone based on the units encumberance.

For Resoln - Wraith Staff - A weapon that take advantage of the Resoln peoples' magical nature. With every strike it does additional magic damage and heals the attacking unit for the same amount.

For Kraxis - Phalanx - A trait. If possible this should require a spear and/or shield. This should provide an activatable ability that forfeits the units turn to gain 1 counterattack + 5 defense and + 5 dodge. This would reflect the defensive strategies they learned while far outnumbered by the fallen and fighting for their lives.

These are just a few examples. Imagine how much flavor this would add to the game if you think about fighting the yithril you know you'll need some archers because you don't want your units anywhere near those greatclubs. You'll remember the bolas of the Tarthan people as your heavy troops end up sprawled on the ground and vulnerable. You might be frustrated trying to get to those kraxian archers. And you'll have to make sure you finish off those Resoln staff bearer units before you start on the next one.

I'm sure there's plenty more ideas that could add to the flavor of each race.