Marco was of above-average height with a broad, muscular build. He had short, parted brown hair, freckles, and light brown eyes. He wore the typical uniform of a member of the 104th Training Corps.

Your Au, have fun : ) 

Eren was a young man of average height and muscular build. He had a fairly long, yet rounded face, and sizable, expressive, teal-green eyes. His eyebrows were sparse and often furrowed, making him seem troubled or annoyed. 

Your Au, have fun 

Jean Kirstein is a highly skilled and talented soldier, though he has an arrogant side. He graduated highly, 6th in his class of the 104th Training Corps. Due to their completely different ideologies and ways of thinking, Jean is often seen butting heads with Eren Jaeger.

Erwin had a commanding presence, standing tall above most members of the Survey Corps, and had a quite muscular build with his blond hair kept neatly parted on the left side. Erwin always wore a calm and collected expression on his face, with his icy blue eyes being one of his most striking features.