Exemplars are incredibly important for showing students what you want them to do--what a high quality piece of work looks like. I have found time and again that they set the bar for my students. The first time I give an assignment is always the hardest, but after that it gets easier. I file away the best ones to use as exemplars when I give the assignment again.
If you are giving an assignment for the first time, though, or are not happy with what students submit, you have a few options. The first option is to take the time to make your own. The second option is to use it as an opportunity to revise. Revisiting assignments and revising them to make them better teaches them to learn from their mistakes and always strive to do better. The third option is to surf the net for online examples. Here are a few sites with exemplars...
#2- The Annenberg Media website has examples of what rigorous foreign language classrooms look like. This website may not have many exemplars to share with students, but there are examples of students engaging in learning to give teachers an idea of what students in a foreign language classroom are capable of.
#3-Online exemplars of work in the arts (drama, visual arts, and music). When you get on the site type the word art in the search.