background image in stringbuilder table

Question

how to add background image in string builder table.

here my code sample 

StringBuilder sb = new StringBuilder();

sb.Append("<table border=1 width = 400 );

sb.Append("<tr width = 20><td width=7% height = 50% width=70% rowspan =4 > </td><td >"+(Reg)+"</td></tr>");

sb.Append("<tr><td>"+(name)+"</td></tr>");

sb.Append("<tr><td>" + (rank) + " </td></tr>");

sb.Append("<tr><td>" + (Aadhar) + " </td></tr>");

sb.Append("</table>");

 

here iwant to add image in table background .