Yes and No.
Graphics are generally final artwork that can only be change with the original files and specialized graphic software with knowledge of its use.
Websites are usually constructed with a Content Mgr system (namely Joomla) allowing you to make updates to pages and images, but probably not the displaying template design.
Video projects are also final artwork edited, and can ONLY be revised and updated with original content, specialized software and knowledge of its use.
So no, most of the time our team must perform this work, and cannot be done by the client. It's not a client-level resource.
Please also note that social networks such as YouTube, etc., do NOT allow the simple "replacement" of a given video, but instead ONLY allow a new upload. What this means is that a video with high subscriptions, for example, will lose its placement in rank and popularity.