Yeah that's what I was talking about. Symbols vs actual units.

I prefer the ones on the right but I believe it's really about opinion and how you view such games. Do you want a more "overlord resource management" feeling where you look at abstraction data like a map with symbols in a tent and tell your messengers to send message about what each unit should do and are only interested in numbers and results. Or are you actually in the same scene witnessing the individual people doing the actions and ordering them as they go.

I believe lots of the problems you are having with creating the art is the fact that all units have the same dimensions and outline where as traditionally stronger units are bigger in pixel size. If you have a clear order of superiority in the units you can also reflect it inside the icon. Weak icon characters could be small with lots of black and strong units could have bigger characters with more white in them so you could also visually grade some battles at one glance even if you needed to further check the types in more depth.

The units on the right are quite nice aesthetically but I still have a hard time telling which unit is which. An RTS might be just twitchy enough that you don't want to sit trying to figure out which units are which. I think you need to make it just as easy to tell what weapon the unit carries as you do the team color.

What about something such that you have the circle the same color for both sides again (perhaps a lighter grey than originally) and then the figures like you have on the right side but in their team color instead of white, and then have the weapon they're carrying another prominent color appropriate to the team? Something so that there's a little more than just the two colors to define the edges.

My art skills aren't that great and I don't know for sure if it would turn out ok but it should be simple enough a change to give it a try.

Another try:)

If i make them much bigger, and use the unit info card (that i already had for each unit type), how does this work? Rough sketchup. This demands that unit move/pathfind in larger tiles, made up of 2x2 maptiles, or that i make the maptiles much larger, which may not look nice...

Wow, you sure have come far from where you started. The icons look great and the critical viewers' attention now turns to lower definition background. :D

I'm sure the players could learn to recognize these icons and intuitively know what they do. If you want to, you can try highlighting ( ~ brightening ) the differences in them (most notably the weapon gear perhaps).

You mean the terrain look blurry? I should redraw the original graphics instead of scale which i do now.

The background around the units could be nicer, and more sharp as well. I think i need this size, as i now have room for healthbar and promotions on each unit.

Personally, I like the weapons symbols more than the person outlines, though those latest images seem distinguishable enough. I just think it gives it a "pure strategy game" feel if the display serves to tell you exactly what you need to know. If you're looking to sell the game though, some visual flare is certainly a good idea.

3. I need to have some health bar on each unit. Any idea on how to avoid it being to cluttered?

Instead of a life bar beneath each unit, you could put a green ring around the unit's circle icon. As they lose health, a portion of the ring turns red. Just make sure the red and green portions won't blend in with either the rest of the unit's icon or the background battlefield.