Emilee, there are several sources about your ancestor (and mine, too). Try your local library for these books:
1. Phares, Ross. Cavalier in the Wilderness: The Story of the Explorer and Trader Louis Juchereau de St. Denis. Baton Rouge: Louisiana State University Press, 1952. (I think this one has a photo of a bust of him located in Natchitoches, LA, and perhaps woodblock renderings of him. It's very scholarly but worth reading for its accuracy.)
2. Ruth, Cross. Soldier of Good Fortune: An Historical Novel. Dallas: Banks Upshaw and Co., 1936. (This book is based on fact but is also a romantic story--fiction.)
3. Title: Natchitoches: The Up-to-Date Oldest Town in Louisiana. (I don't have the rest of the bibliographical information for this one, but if you can't find the book, let me know and I'll dig up the rest of the information for you. This book actually has a family tree in it--a cool find.)
Other sources are available, but none have pictures or renderings of the family. But these will offer descriptions of them. If you do find portraits or drawings of the family, please let me know; I'd love to have a copy of them, too.
Let me know what you think of these sources.