Paintings can be viewed here:
http://emelyan.ru/pamjat/istoricheskie-kartiny-posvjashhennye-pugachevskomu-vosstanijuYes, this figurines can be used.
"Uniform" of the rebels (according to the book by Zemtsov V.N., Lyapin V.A. "Ekaterinburg in uniform"):
This is what the Cossacks looked like a little later.
The Yaitsky (later - Ural) Cossacks (like all others) at that time did not have an approved uniform, but they observed a certain "Cossack" style of dress. The Cossacks at that time were prescribed certain colors in military clothing, but this was not strictly observed, although this color still prevailed.
The Ural Cossacks (the bulk of the rebellious Cossacks, although there were Don, Volga, Orenburg, Astrakhan and other regiments among them) were supposed to have light blue caftans and trousers, raspberry sashes and a raspberry top fur hats.
The Don Cossacks were prescribed blue caftans, bloomers and tops of hats. Moreover, the caftans had red collars, cuffs and lining (inside out). Crimson sashes (belt scarves) with red fringe.
The Volga Cossacks wore mostly red clothes with a blue sash.
Orenburg - like the Don, but with a black sash.
The Astrakhan Cossacks were dominated by a dark brown color, sashes were blue.
As a rule, all Cossacks had caftans trimmed with narrow yellow braid.
The officers had gold trim on their caftans and on the top of their hats. Their sashes were either embroidered with silver and gold, or were generally gold and silver. The officers' boots were made of colored leather (red or yellow). For ordinary Cossacks, boots are mostly black. Hats - from gray or black fur for all Cossacks.
The Cossacks were armed with sabers with a copper or iron frame, pikes with a red shaft, guns of arbitrary designs, often Turkish or Persian. The officers' weapons were decorated with silver and gold.
The banners were of various colors, but made according to the same pattern, they carried the image of an eight-pointed Orthodox cross.
Prosperous Russian peasant of the 18th century
The infantry consisted of peasants, as well as a considerable number of deserters from the tsarist army (these often wore elements of military uniforms). Peasants wore traditional peasant clothes. The predominant color is homespun cloth, light gray, rarely black. Wealthy peasants could have clothes made of colored cloth - blue, brown or cherry.
They were poorly armed, there were few firearms. The main weapons are spears, clubs, axes and the like.
The banners (one per regiment) were mostly made of yellow or red silk with a straight cross sewn on, less often the face of the Savior or Nicholas the Wonderworker.
There was also one “real” banner - the Delvig Dragoon Regiment (from the Holstein troops of Peter 3, for whom Pugachev pretended to be).
Pipes and drums were not used
Most Cossacks and all peasants wear beards.
Pugachev's army was divided into regiments, regiments into companies. But discipline, especially in non-Cossack units, remained rather weak.
Artillery did not have a definite organization and was the most diverse, captured in the garrisons of subordinate cities, from defeated army units, and also made specifically for the rebels at the Ural factories by the insurgent workers.
Bashkirs, Kalmyks and other militias of non-Russian nationalities have national clothes. You can use figurines for 1812 in national costumes (not in official uniform).
I will describe the weapons and uniforms of government troops later.