I would definitely include SIJ. I don't know why so many people here are saying you can't get paid for it. You most definitely can. You just can't bill it as a typical SI joint. It is supposed to be billed as a TP injection. I do these all the time. Surprisingly, in my elderly patient population, I've had better success with US for these than with fluro. It's also really easy to learn to do. I agree with all the other posters here that standard joint injections would be very helpful, specifically both shoulder and hip. I would also include lat and med epicondylitis injections and carpal tunnel injections. Even though facets aren't covered yet, things may change in the future. There have been a handful of patients I have done this for who were in their 90's and were in such crippling pain, they couldn't lie prone on the procedure table. I was able to do US lumbar facets with the patients in a seated position, which worked well enough for them to be able to have a 'proper' fluro-injection a week later. SS is another one that comes in very handy and is fairly easy to teach. Intercostal is another great one, especially if taught right with explanations for preventing and diagnosing PTX, Thoracic TPI's is then intuitive.
Personally, I think it's imperative to learn US basics before jumping to procedures, especially advanced procedures like many of the ones mentioned here. As a resident, I took several diagnostic US courses, then would practice on myself during lunch breaks and in clinic on patients. I probably read more articles on US technique than any other MSK subject. Only after I felt comfortable really being able to differentiate between all anatomic structures did I start injecting. I went to one advanced procedure course, and there were only a handful of us there who actually had any experience with US. We were all fine and picked up the new techniques fairly quickly. It definitely seemed to me though that the others were pretty lost. I highly doubt any of them incorporated any of the procedures taught into their practices. My point is that I highly recommend a preliminary US basics course.