If you are creating folder at runtime, how can there be images in that?
Anyways, here is how you can create a directory at runtime
IO.Directory.CreateDirectory("C:\\MyImages");
And this is how you can get all jpg images from that folder.
DirectoryInfo di = new DirectoryInfo("C:\\MyImages");
FileInfo[] fi = di.GetFiles("*.jpg");
Try to work out your problem with this.