Hi
I work in mental health and would agree that there are various issues/challenges which could be very well presented as a poster.
1. A very challenging client group.- you could work for the olympic team or a very busy outpatient department where the majority of your caseload are highly motivated individuals. In MH, you are working with a group who are not motivated, lack confidence or even looking to self harm. The challenge is how you ensure that these people comply to your treatments and recommendations, hence job satisfaction is very hard to come by, which means
2. Therapist views and attitude is very important.-This to me is the bullseye. You could be a great physio with plenty of knowledge but if you lack the attitude, then you are useless. The qualities of a MH physio is to be very patient and persistent with your approach ensuring that something is delivered for the benefit of your patient. The Ability to think out of the box and sometimes focus on a holistic method.- I personally think this is the way to go. Using various complementary therapies as an adjunct to physiotherapy can be very rewarding. Therapies such as swedish massage, reflexology, Acupuncture, acupressure, relaxation therapies, etc can be very useful
Good skill in the use of exercise and ability to promote physical activity are other avenues which can also be added strings in the bow of a Mental health physio.
The bottom line is - to be a good MH physio you've got to be a Jack Of All Trades.

I feel physios should be more pro active in their approach and take up more responsibility and upgrade themseves as health promotion specialists.
Hope this can sum up what you are looking for.
cheers
JP