The Uniformes Militares Espa�oles site has extensive color plates of Spanish Uniforms for the years 1800 – 1980.
I know you won’t believe me, but there’s more to painting Austrian Napoleonic uniforms than endless seas of white. You can find more details in the uniform guide here.
There are some nice color plates on this site showing the uniforms of the German states in the 1700s. I don’t know German, but by looking at the plates, I think that they’re all from the Seven Years War. The first page is definitely Frederick the Great and his generals. Someone with more epertise in either the period or in German will have to provide more detail.
The Sons of the Revolution in California have produced a fabulous set of pages with color plates of the uniforms of the American War of Independence. There’s a list below of the units that they have:
Uniforms of the American Revolution; American Farmers Forming at Concord; Sherburne’s Continental Regiment, 1778 – 1780; Moylan’s Light Dragoons, 1779; Second
Canadian Regiment of Infantry, 1776; Fourth Connecticut Regiment of Infantry Continental Line; Second Regiment of Connecticut Light Horse Militia, 1777; Haslet’s Delaware Regiment, 1776; First Georgia Regiment of Infantry Continental Line, 1777; Smallwood’s Maryland Regiment, 1776; Second Maryland Regiment of Continental Infantry, 1777; Fourth Independent Company of Maryland State Troops, 1776; Second Massachusetts Regiment of Continental Infantry, 1777; Massachusetts Regiment of Artillery, 1775-1776 — Knox’s Artillery; Second New Hampshire Regiment of Infantry, 1777 Continental Line; Third New Jersey Regiment, 1777 Continental Line; Third New York Regiment, 1775, Continental Line; Captain John Lamb’s New York Artillery Company, 1775; Third North Carolina Regiment of Infantry, 1778 Continental Line; First Pennsylvania Battalion, 1775 – 1776; Pennsylvania State Regiment, 1777 – 13th Pennsylvania Line; Rhode Island Train of Artillery, 1775; Second Rhode Island Regiment of Infantry, 1779; Second South Carolina Regiment of Infantry, 1776; Green Mountain Rangers, 1776; Lt. Ira Allen’s Green Mountain Rangers, 1775; Virginia Light Dragoons, 1776; Independent Companies, 1775; Miscellaneous Organizations, Continental Army, 1776; Commander-in-Chief and Line Officers, 1779; Continental Infantry, 1779-1783; Continental Artillery, 1777-1783; Light Infantry, 1782; Infantry and Artillery, 1783; Sir William Howe, Commander-in-Chief of the British Armies in America; British Seventeenth Regiment of Light Dragoons, 1775-1783; Musicians of the British Fourth Regiment of Foot, 1778; Grenadier Company, Fifth Regiment of Foot, 1776; Light Infantry, British Tenth Regiment of Foot, 1775; Drummers, British Tenth Regiment of Foot, 1775 – 1783; Royal North British Fusileers; Light Infantry Company, British Fortieth Regiment of Foot, 1776; British Forty-Second Regiment of Foot, 1776; British Forty-Third Regiment of Foot, 1775; Grenadiers, British Fifty-Second Regiment of Foot, 1775; Butler’s Rangers, 1777; De Lancey’s Brigade, 1776 – 1783; De Lancey’s Refugees, the "Cowboys", 1780; Emmerich’s Chasseurs, 1776; Johnson’s Royal Greens of New York, 1776; Queen’s Rangers, 1776-1783; Grenadiers, Gatinois Regiment of Infantry, 1781; Saintonge Regiment of Infantry, 1781; Saintonge Regiment of Infantry, 1779-1783; Field Yager Corps of Hesse-Cassel, 1776-1783; Hesse-Cassel and Brunswick Regiments, 1776-1777; Grenadier Regiment Von Rall, and Fusileer Regiment Alt Von Lossberg of Hesse-Cassel, 1776; Fusileer Regiment Erb Prinz of Hesse-Cassel, 1776; Independent Company Organizations: Goot-Guard, Virginia Riflemen, Minutemen, 1774-1775; Privates of Light Infantry and Drummer: 10th, 14th and 42nd British Foot, 1775-1783; Privates and Officers of De Lancey’s Brigade and of Johnson’s Royal Brigade of New York, 1776-1781; Privates of von Rall’s and von Sprecht’s Regiments and Field Jager Corps, 1776-1783; Privates in Field and Parade Dress, Smallwood’s Maryland Regiment, 1776; Continental Artillery, 1777-1783; Privates of 2nd and 4th Connecticut Regiments, 1777; Privates, Continental Line with Artillery Officers Second Massachusetts Regiment, 1777; Sir William Howe, Commander-in-Chief of the British Army with 4th Regiment of Foot, 1775-1778; Gatinois and Saintonge Regiment of Infantry in Parade Dress, 1781; Commander-in-Chief, and Staff, 1799-1802; Cavalry, Infantry and Artillery 1799-1802; Continental Navy, 1776-1777;
The Princely States Report website has some neat color plates of Indian Army unforms from the 1930s and 1940s. They’re originally from a pack of 50 Players Cigarette Cards.