The unfortunate thing about Catherine the Great, at least when it comes to TV and or movie adaptations, is that the most famous ones tend to be from Hollywood. Since the most accurate depictions of historical figures are always going to be by state-owned TV stations from their country of origin, expect any English-language adaptations of Catherine’s story to be historically inaccurate.
I can’t be bothered to list any non-Russian productions, but luckily, there are two Russian-language TV series that is worth watching (not least because some of these will be filmed at actual historical locations such as the Winter Palace and Oranienbaum). The first is Ekaterina (2014), made by state-owned Russia-1, which as of this article has 3 season that cover most of Catherine’s reign. The other is Catherine the Great (2015), broadcast on Channel One Russia, also a state-owned TV channel, with 2 seasons.
It’s not easy finding English subtitled versions for these two series, but clips on Youtube abound. Here are some samples from both series.
Apart from TV series, there are many portraits of Catherine the Great and various courtiers that was painted in her time. There are also a number of paintings from her era that depict her doing certain things, and a number of her gowns have also been preserved by the Russian State Heritage Museum. Countless photos of these can be found online.