Studied art, Munich, Germany, and Italy, 1857-1859.
He designed the original Confederate flag, the Stars and Bars, as well as the official grey uniform of the Confederate army. He emigrated to the United States in 1849 through New Orleans, Louisiana, headed for the home of a relative in Mobile, Alabama. In 1851 he relocated to Marion, Alabama, where he began teaching art first at his portrait studio, and then at the Marion Female Seminary.
During this time he briefly returned to Germany to further his art technique. Mary Clay Lockett, wife of prominent Marion attorney Napoleon Lockett, requested Marschall to take part in the competition to create a new flag to represent the Confederate States of America. Marschall's design became the first Confederate flag, first raised in Montgomery, Alabama, on March 4, 1861.
During the Civil War Marschall served in the Second Regiment of Confederate Engineer Troops, under Samuel Lockett. During his career he painted portraits of Jefferson Davis, Abraham Lincoln, Otto von Bismarck, various Southern families, and Confederate and Union soldiers. He was one of the few who was able to have Nathan Bedford Forrest pose for him.
Additionally, he did many landscapes and religious paintings. He was known to sign and date his portraits using a steel pen while the paint was still wet, at the bottom-right of the portrait. Due to the economic depression in the South following the war, he returned to Mobile in 1872.
In 1873 he and his family moved to Louisville, Kentucky, as his friends told him it would be an easier place to gain commissions to do portraits. In 1908 he gave up working on portraits. He died in Louisville on February 24, 1917, and was interred in Cave Hill Cemetery.