Concept Art for the Early Mardi-Gras

Assuri” costume design by Carlotta Bonnecaze for the
“Myths and Worships of the Chinese” theme, Krewe of Proteus, 1885:
Carnival Collection, Louisiana Research Collection, Tulane University — Source

In the 19th century, concept art for the Mardi Gras celebration of New Orleans drew inspiration from an eclectic variety of religions and design traditions—everything from Chinese mythology, to South Asian deities, to dragons from European folktales.

Bat costume designed by Charles Briton for the “Missing Links”
theme, Mistick Krewe of Comus, 1873: Carnival Collection,
Louisiana Research Collection, Tulane University — Source

The theme of the 1873 parade was “Missing Links to Darwin’s Origin of Species,” with a gentle satire of the ideas that were circulating at the time.

Scorpion costume designed by Charles Briton for the “Missing Links”
theme, Mistick Krewe of Comus, 1873: Carnival Collection, Louisiana
Research Collection, Tulane University — Source

The teams of designers competed with each other to come up with the most creative and outlandish  creatures.

“Such Stuff as Dreams are Made of” float design by Jennie Wilde for the
“Familiar Quotations” theme, Mistick Krewe of Comus, 1911:
Carnival Collection, Louisiana Research Collection, Tulane University — Source 

There were also extravagant floats in the early Mardi Gras, and many of them were designed by women, such as Jennie Wilde, who drew inspiration from Art Nouveau and the Symbolists.

From the Louisiana Digital Library

A float from the Louisiana Mardi Gras parade conjures crashing waves, seabirds, and seahorses.
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From the Public Domain Review
The blog Lines and Colors featured the dragon paintings of carnival artist Bror Anders Wikstrom
Through April 1, the New Orleans Museum of Art is featuring an exhibition of Wikstrom's carnival art.
Books:
Mardi Gras Treasures: Costume Designs of the Golden Age Notecards
All on a Mardi Gras Day: Episodes in the History of New Orleans Carnival