If one looks closely to panels one and four of Sten's portraits, one can see how his eyes, nose and mouth are slightly twitching. It's minimal but the effect is fantastic! In panel 4 he looks something in between of surpressing a sneeze and surpressing a 'I'm being tickled'-face. And your Brosca is lovely!
I always liked how sten conversations were a lot more complicated with how you had to handle him compared to other characters.
Most other bioware guys/gals, you have to butter them up pretty up all the time, every time. Sten actually has more respect for you if you give him a little back talk, though not every time, so it's not quite as simple as always picking the most combative response.
It would be nice if more of the relationships were that complex.