I've just finished the final scenario and decided to give you a rather detailed feedback, since it was a great campaign and it deserves every minute of my time to be reviewed. I'll start with worse stuff, so I don't live a bitter aftertaste
This was mentioned before, but this really is an issue you should work on. It just makes it too easy...
You really have to do something with gold. Especially after that scenario where you get rewards for assassination. After that scenario you have ridiculous amount of gold to spend on very cheap units. I thought that soon there will be some great battle, but it never came. So I ended up with enormous amount of gold wasted because of carry over percentage. I was playing on medium but it felt like sandbox because I finished every scenario with hundreds of spare gold (that means dozens of units I could have recruited).
At first they were pretty fun, because they were free xp for my goblins but further in campaign they were simply annoying, because they only blocked my units posing no threat whatsoever to my army.
That was one of those things that annoy player and don't add any real difficulty to the scenario. I discovered that merman with pillager and when she asked me for my leader I've made Clannie leave the battlefield and go back to that stupid merman only to find out it was a ghost who wanted to kill me. I had to load game from 8 turns before
Loot ability (bug?)
I've noticed that after you kill someone using loot attack you get an extra turn for your victorious unit. I'm not sure if it's planned or if it's simply a bug.
Dire wolf attacks
I have a silly question. Why does dire wolf unit have two blade attacks, one with lower damage (claws)? It seems like you didn't finish something- perhaps claws should have poison or impact?
That's about it. Overall, it was a great campaign, very enjoyable. Good plot, well made scenarios. It just had this something that makes a campaign special. Very, very, VERY good job!
One more thing: I've noticed that you lack sprites. Would it be possible to let me try and make some? I've never done it before and because of summer break I have lots of time. Cheers!