I always and have forever been using stigs background image tool at http://backgrounds.cm!.
Recently some people in my office started seeing emails in outlook 2016 looking messed up. See the example below
Example
Here is my code

<tr>
<td background="http://static.cdn.responsys.net/i5/responsysimages/content/vervesub/Email-hb5%202.png" bgcolor="#fff" width="600" height="535" valign="top" style="background-repeat: no-repeat;background-position: center top">
<!--[if gte mso 9]>
<v:rect xmlns:v="urn:schemas-microsoft-com:vml" fill="true" stroke="false" style="width:614px;height:540px;">
<v:fill type="frame" src="http://static.cdn.responsys.net/i5/responsysimages/content/greensmoke/VRV889_1.jpg" color="#fff" />
<v:textbox inset="0,0,0,0">
<![endif]-->
<div>
<table cellpadding="0" cellspacing ="0" border="0" align="center">
<tr>
<td class="one-column" style="padding-top:0px;padding-bottom:0;padding-right:0;padding-left:0;" ><table width="100%" style="border-spacing:0;font-family:sans-serif;color:#ffffff;" >
<tr>
<td class="inner contents" style="padding-top:200px;padding-bottom:10px;padding-right:10px;padding-left:10px;width:100%;text-align:left;" ><p class="h1" style="Margin:0;color:#fff;font-weight:bold;font-size:14px;Margin-bottom:10px;" >&nbsp;</p>
</td>
</tr>
<tr>
<td class="inner contents" style="padding-top:80px;padding-bottom:0px;padding-right:10px;padding-left:10px;width:100%;text-align:center;" ><p class="h1" style="Margin:0;color:#F5780D;font-weight:400;font-size:29px;Margin-bottom:15px;font-family: Arial, sans-serif,'Cabin';letter-spacing: 0px;" >We've Got Flavorful News</p>
<img src="http://static.cdn.responsys.net/i5/responsysimages/content/greensmoke/harvestblend.png" width="321" alt="Harvest Blend" style="color:#f5780d; font-size:border-width:0;width:100%;max-width:320px;height:auto;" />
<p class="h1" style="Margin:0;color:#F5780D;font-weight:500;font-size:20px;Margin-bottom:30px;font-family: Arial, sans-serif,'Cabin';letter-spacing: 0px;" >is now available at ChewOnVerve.com</p>
<p class="h1" style="Margin:0;color:#000;font-weight:700;font-size:16px;Margin-bottom:10px;font-family: Arial, sans-serif,'Cabin';letter-spacing: 1px;" >A bold mix of cinnamon and spice<br>with a warm finish</p></td>
</tr>
</table></td>
</tr>
</table>
</div>
<!--[if gte mso 9]>
</v:textbox>
</v:rect>
<![endif]-->
</td>
</tr>