First you should save as picture in your Image from Picture Box.
And then you can pass your existing image file path as string ,
string imagepath = "file:///" + "C:\\image.jpg";
this.reportViewer1.LocalReport.EnableExternalImages = true;
ReportParameter[] param = new ReportParameter[1];
param[0] = new ReportParameter("Path", imagepath);
this.reportViewer1.LocalReport.SetParameters(param);
this.reportViewer1.RefreshReport();
In rdlc file you create Image box and then add Report parameter (Path).
After you add parameter you can insert in image value from parmaeter(Path).
May be helpful,
Theingi Win