For me, Thane didn't come to the tavern until after I had brought peace to both sides. Before that, I was on the Thane/Nauxus route and had been asked to deliver the poison toadstools. I did not deliver the toadstools since that would have triggered the ending where Thane and Axel die. Instead I wandered around until I was delivered Thane's bloodied cloth. I don't remember if I received it while in the tavern or the bull's camp. After I received it, I was able to enter the pictures, find the shapeshifter, and end up with the 'good' route where both Thane and Nauxus were at the tavern.