Since we don't have a CDN url setup. I created this patch file and now I am getting results as expected.
<?xml version="1.0" encoding="utf-8" ?>
<configuration xmlns:patch="http://www.sitecore.net/xmlconfig/">
<sitecore>
<settings>
<setting name="Media.RequestExtension">
<patch:attribute name="value"></patch:attribute>
</setting>
<setting name="Media.MediaLinkPrefix">
<patch:attribute name="value">customname</patch:attribute>
</setting>
</settings>
<customHandlers>
<handler trigger="/customname/" handler="sitecore_media.ashx"/>
</customHandlers>
</sitecore>
</configuration>
Now I am getting below results:
"Image": {
"src": "/customname/images/abc.jpg",
}