I contend that images (files) are NOT usually stored in a database base64 encoded. Instead, they are stored in their raw binary form in a binary (blob) column (or file).
Base64 is only used as a transport mechanism, not for storage. For example, you can embed a base64 encoded image into an XML document or an email message.
Base64 is also stream friendly. You can encode and decode on the fly (without knowing the total size of the data).
Do not store your images base64 encoded.