No one can give you serious feedback on improving the taste and/or texture of your panna cotta and/or your mango coulis because you didn't describe them. If you want help you need to give some description of what you did to make the dish and how it turned out. Recipes are helpful, especially if you're a recipe driven cook or are unsure if the problems are the result of the recipe or your own technique; however, they're not always necessary.
Koukouvagia is right about the size of the glass. The largest problem with your presentation by far was that the glass was too way too small for the portion. As a rule of thumb, you can put a small dessert on a big plate but not in a big glass; and in a wide diameter bowl, but not in one of small diameter. Your guests should not have to start eating their sweet by digging for it.
Assuming you didn't have cocktail or dessert glasses of the right side, panna cotta should be stiff enough to hold its shape on a plate (or in a large bowl). If you did that, the most typical (and admittedly somewhat dated) way to plate would have been on top of a puddle of the coulis.
The solutions to the plating problem are so obvious that your service leads to the following questions: What do you mean by describing yourself as a "culinary student?" Are you cooking at home, taking cooking in a secondary school, at a post-secondary professional culinary school, or some combination?
I ask because if I'm going to give you advice, I'd like to pitch it to the right level and yours seems -- no criticism intended -- both naive and opinionated.
Edited by boar_d_laze - 12/1/12 at 10:12am