You will have to translate the steps here into ones specific for your image program. For this example, I'm using Paint Shop Pro 8.
Choose your new unit image. Open it, and also 'promotion_frame.png' 'unit_artspace.png' and 'unit_bevel.png' in your image editor program. These images are found in C:\Program Files (x86)\Steam\steamapps\common\Sovereignty Crown of Kings\Tools\Art
Select a square region of your new unit image and copy/paste it as a new image.
Resize the new image to be 150 x 150 pixels and save it as a .jpg image on high quality.
Add a new mask layer to this image 'From Image' and choose the source image as the 'unit_artspace.png' and selct 'Create Mask From Source Opacity'.
If you've done it correct, the image is now a circle, with blank space surrounding it.
Select 'Layers' and 'Merge Visible'. It is now one layer. This is your basic image which will now be used with the 'promotion_frame.png' and 'unit_bevel.png'.
Copy and paste the basic image onto the 'unit_bevel.png' and make sure the 'unit_bevel.png' is the top layer. You will have to drag the image layer around a little to match it up.
Do the same again for the 'promotion_frame.png'. Make sure this is the top layer. You will have to take the eraser and delete the parts of the basic image that are outside the edge of the frame.
Now save the 'promotion_frame.png' and 'unit_bevel.png' as png files, choosing to save with alpha channel transparency and using existing image or layer transparency.
You should have three new images with your new unit on. Make sure you rename them to the name of your new unit, e.g. 'barbarian_warrior.'
Here's where they are placed.
150x150 jpg placed in:
Documents\Sovereignty\Mods\Your Mod Name\Images\Units
'promotion_frame.png' placed in:
Documents\Sovereignty\Mods\Your Mod Name\Images\Units\promotion
'unit_bevel.png' placed in:
Documents\Sovereignty\Mods\Your Mod Name\Images\Units\Combat
Hero units use the ''promotion_frame.png'' and are placed in:
Documents\Sovereignty\Mods\Your Mod Name\Images\Units\HeroHire
They also use a 150x150 jpg and are placed in:
Documents\Sovereignty\Mods\Your Mod Name\Images\Units\Units\Hero
Landmarks and terrain images are 180x120 png files and are placed in
Documents\Sovereignty\Mods\Your Mod Name\Images\HUD\landmarks
