Detail from Gustavus Adolphus at Breitenfeld Johan Walther, c. 1632

 Battle of Breitenfeld (1631) - Wikipedia

Kroatischer Reiter mit schwarzer Krawatte um 1630 (Heeresgeschichtliches Museum, Wien).

 

Johann Ludwig Hektor von Isolani

 Wallenstein's first Croat cavalry commander. Johann Ludwig Hektor von Isolani – Wikipedia

Peter Snayers - Het beleg van Einbeck door Ottavio Piccolomini en aartshertog Leopold Wilhelm, 20-24 oktober 1641

 

Imperial Armies of the Thirty Years' War

 Croats. Pic by Darko Pavlovic from the Osprey.

The Halt of the Cavalry by Flemish artist Peeter Snayers

 Croats. Peter Snayers - Wikipedia Thanks to Vladimir Brnardić for this.

Croatians in the Thirty Years War (Military Illustrated)

 M I Past Present 1993 63. : SKORPIO : Free Download, Borrow, and Streaming : Internet Archive

Cavalry on the march Marcellus Laroon the younger

 Marcellus Laroon the Younger - Wikipedia

Croats in the 30 Years War

When I had a Habsburg TYW army these were difficult figures to source.

Wars of Louis Quatorze: Carlo Fantom - a famous Croat in the English Civil War

Art from Lützen 1632: Climax of the Thirty Years War, illustrated by Graham Turner

The Croats, also known as Cravats or Crabats, were 17th-century light cavalry forces in Central Europe, comparable to the hussars. They were initially irregular units loosely organized in bands and the first regular Croat regiment was established in 1625. The most notable engagement of the Croats was their participation on the Habsburg side in the Thirty Years' War, serving in the Imperial Army or within the troops of the Catholic League. At the height of the Thirty Years' War, as many as 20,000 Croatian cavalry were in the service of the Imperial Army, including the majority of Wallenstein's harquebusiers. The name "Croats" became a generic term for light cavalry from the Habsburg Military Frontier rather than an ethnic designation, and included ethnic Croats, Hungarians, Serbs, Wallachians, Poles, Cossacks, Albanians, and Tatars. The Croats were initially recruited by generals of the Habsburg monarchy, and soldiers who joined Croats signed contracts which expired after the military campaign would be over, most often for any booty and sometimes for a fee. 

Wikipedia+2

Croats

 Zagreb. Traditional New Year's Change of the Guard Kravat pukovnija ! Traditional new years change of the guard of Kravat regiment! Thanks to Vladimir

Rene Chartrand's Military modelling articles in the 80s

 Back in the 80s before the Louis XIV's army Osprey came out (1988) the best place for information on the Sun King's forces was in  a series of articles written by Chartrand in Military modelling magazine. I remember having them safe in a file though I can't find them now. But we still have the accompanying illustrations which were done by the usual M.M. artists.

Carlo Fantom - a famous Croat in the English Civil War

Carlo Fantom (died December 1643) was a Croat mercenary in the English Civil War who had the reputation of being impervious to bullets and is quoted as saying "I care not for your Cause; I come to fight for your halfe-crown and your handsome women. My father was a Roman Catholique, and so was my grandfather. I have fought for the Christians against the Turkes, and for the Turkes against the Christians." Initially serving in Arthur Goodwin's regiment of horse, where he was valued by the Earl of Essex for training cavalrymen how to fight on horseback, in 1643 he changed sides to fight for the King. He was reportedly hanged at Bedford for raping a woman, while the army was marching to relieve Gainsborough.^[1] Wiki
If you think this would make great fiction it's been done by Charles Underhill. Not sure what they're like. Maybe you know?