Warning - lots of images!
Open the Mod Helper; it defaults to the SGA Extractor view (as this is the first step in getting to most of the game's assets). If you don't have your own directory for cope's SGA Extractor command-line tool (you will need to set the folder manually in this case), my Mod Helper does come packaged with it.
Then you need to set the location of any SGA archives you want to extract from. For example, the default game directory for its archives is (for my Steam install):
X:\SteamAlternative\SteamApps\common\Dawn of War III\DoW3\archives
This will then populate the dropdown with all SGA archive files found in that folder.
Select the one you want to extract, and then set the output folder (which can be anywhere you want).
You should then have a view that looks something like this one:
Once you hit "Convert selected", you can track the progress by the bar at the bottom. cc2sga.exe doesn't provide much programmatic feedback, so for the larger archives (or ones with lots of files inside) you may be waiting a while here.
At the end it should tell you how many were extracted (this line is directly from the cc2sga.exe tool).
And you're done! Do with the resulting files what you want
Complete imgur album link here.