public HttpResponseMessage GetPictureById(string id)
        {
            if (id.ToLower() == "random")
            {
                id = GetRandomImageId();
            }

            var file = GetFile(id);

            if (file == null)
            {
                return(new HttpResponseMessage(System.Net.HttpStatusCode.NotFound));
            }

            var content = HttpResponseExtensions.CreateFileContent(file);

            return(new HttpResponseMessage(System.Net.HttpStatusCode.OK)
            {
                Content = content
            });
        }