A working example of how to add an image via the API.

Upload_Image_To_CMS.cs

var filePath = Environment.GetFolderPath(Environment.SpecialFolder.UserProfile) + "\\Pictures\\";

var fileName = filePath + "bobafett.jpg";
var properties = new JObject();
properties.Add("height", 300);
properties.Add("weight", 300);

var documentResource = new Mozu.Api.Resources.Content.Documentlists.DocumentResource(_apiContext);
var document = new Mozu.Api.Contracts.Content.Document()
{
    Name = "bobafett.jpg",
    DocumentTypeFQN = "image@mozu",
    ContentMimeType = "image/jpeg",
    Extension = "jpg",
    Properties = properties
};

var file = System.IO.File.OpenRead(fileName);

document.ContentLength = file.Length;

var addedDoc = documentResource.CreateDocumentAsync(document, "files@mozu").Result;

documentResource.UpdateDocumentContentAsync(file, "files@mozu", addedDoc.Id).Wait();