Managing subfolders in media library
If you have a lot number of images, you can use FileBird – WordPress Media Library Folders to organize it. I'm currently using FileBird for all my client project.
Here is a screenshot so you can easy to understand how it works.
I'm using Pro version here https://codecanyon.net/item/media-folders-manager-for-wordpress/21715379 but if you need around 10 folders, free version is enough.
One more thing I love FileBird is the support team is very nice, they support fast and you can live chat with them on their FB fan page.
I hope it's useful for you.
Indeed, there's a plugin for that, but it's old (last updated in 2008) and seens to only accepts custom names based on wordpress variables. (%year%, %month%, etc).
In my opinion, you could use it and adapt to your needs with some coding.