Images that reside in the grid will get resized (scaled down with about 3-5 %) which might cause issues, specially if exporting bar-codes, thus the bar-code scanners won't be able to read them.

Current workaround is to use the Telerik Documents Processing Library  and build the table manually where the images are inserted without changing the size.

Here is an example:

        protected void RadGrid1_InfrastructureExporting(object sender, GridInfrastructureExportingEventArgs e)
        {
            Telerik.Web.UI.ExportInfrastructure.Table table = e.ExportStructure.Tables[0];

            Workbook workbook = new Workbook();
            workbook.Worksheets.Add();

            Worksheet worksheet = workbook.ActiveWorksheet;


            foreach (var row in table.Rows)
            {
                if (row.Index > 1)
                {
                    worksheet.Rows[row.Index - 1].SetHeight(new RowHeight(55, true));
                }

                foreach (var cell in row.Cells)
                {
                    if (row.Index == 1 || cell.ColIndex != 2)
                    {
                        worksheet.Cells[cell.Index.Y - 1, cell.Index.X - 1].SetValue(cell.Value.ToString());
                    }
                    else
                    {
                        FloatingImage image = new FloatingImage(worksheet, new CellIndex(cell.Index.Y - 1, cell.Index.X - 1), 0, 0);
                        Stream stream = File.Open(Server.MapPath(cell.Value.ToString()), FileMode.Open);
                        using (stream)
                        {
                            image.ImageSource = new Telerik.Windows.Documents.Media.ImageSource(stream, "jpg");
                        }
                        worksheet.Shapes.Add(image);
                    }
                }
            }

            byte[] data;

            using (MemoryStream ms = new MemoryStream())
            {
                XlsxFormatProvider xlsProvider = new XlsxFormatProvider();
                xlsProvider.Export(workbook, ms);
                data = ms.ToArray();
            }

            Response.ContentType = "application/vnd.openxmlformats-officedocument.spreadsheetml.sheet";
            Response.Headers.Remove("Content-Disposition");
            Response.AppendHeader("Content-Disposition", "attachment; filename=" + RadGridLista.ExportSettings.FileName + ".xlsx");
            Response.BinaryWrite(data);
            Response.End();
        }