Here is working code for converting an image from a base64 string to an Image object and storing it in a folder with unique file name:
public void SaveImage()
{
string strm = "R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7";
//this is a simple white background image
var myfilename= string.Format(@"{0}", Guid.NewGuid());
//Generate unique filename
string filepath= "~/UserImages/" + myfilename+ ".jpeg";
var bytess = Convert.FromBase64String(strm);
using (var imageFile = new FileStream(filepath, FileMode.Create))
{
imageFile.Write(bytess, 0, bytess.Length);
imageFile.Flush();
}
}