Are you wanting “feature request” for something that doesn’t exist?
Or, are you wanting to know how to upload an image file?
The API documentation is kind of dumb, in that it says you upload a file object - and that the endpoint returns the file object.
In a way, the files endpoint does accept base64, because what you must send is a multipart/form-data POST https request, where the file is MIME attachment of type image/png, with file name. Knowing this, your Google search for some code will have answers.
Part of the “form” is to send the purpose of the file, also.