CSS Circle // Border Radius

<table cellpadding="0" cellspacing="0" border="0">
  <tr>
    <td align="left" valign="top" style="background-color:#FF0004;"><img src="http://placehold.it/100x100" alt="" width="100" height="100" border="0" style="display:block; border-radius:50%;" /></td>
  </tr>
</table>

For a Border Radius with a Border

<table cellpadding="0" cellspacing="0" border="0" style="border-collapse: separate !important;">
  <tr>
    <td width="100" height="100" align="center" valign="middle" style="font-family:Helvetica, Arial, sans-serif; font-size:10px; mso-line-height-rule:exactly; line-height:12px; color:#8b6d49; padding:0 0 0 0; border:1px solid #8b2331; border-radius:50%;">
      EXAMPLE
    </td>
  </tr>
</table>