Is it better to have a default avatar library on client or server side?

I have a webapp using ReactJS as the frontend and Rails as the backend service.

I have an account manager, where a user can choose multiple avatars from a default library. This library contains around 250/300 images, and uses 20Mb of disk space.

I was wondering whether it is a good thing or not to have them stored on the client side. I believe that client side storage is easier to update, since I can just add/remove/rename files from my explorer during development.

However, I hesitate quite a lot, since I am aware of possible performances issues from memory usage. Plus, once uploaded to server, images can be easily retrieved as a URL list, and I won’t have to use file libraries like fs. But it’s a pain to upload them all, not to mention I’ll need to use a specific database manager each time I need to update/add/remove a file.

Which is the best practice for this particular case, and given the libraries in use (ReactJS and Rails)?