Image is a file entity and to make it fieldable you can use this module:
File Entity (fieldable files)
From the documentation:
The File entity module extends the capabilities of the core File
File Entity defines 5 File Types - Application, Audio, Image, Text,
Video. The Media module adds an additional File Type - Other
(currently these File Types are hard coded and cannot be changed).
When files are uploaded they are automatically assigned the
appropriate File Type based on the file suffix.
The File Types as currently defined are:
Images - .png, .gif, .jpg, .jpeg, .ico Videos - .mov, .mpg, .flv,
.m4v, .mp4, ,ogg, .ovg, .wmv Sound files - .mp3 Text - .txt Document
files - .doc, .xls, .pdf, .ppt, .pps, .odt, .ods, .odp Other - ??
Each File Type can have fields. This allows for additional information to
be stored along with a media file such as Title, Description, Taxonomy
References, Node References, Location, Date created, License