SharePoint Designer: Embedding Image in Workflow Mailer

1. Create a Pictures Library in SharePoint.
2. Add the required image in the library and copy the image URL.
3. Create workflow in SP Designer.
4. Create a workflow variable with datatype as string.
5. Assign variable following value:

<img src="ImageURL" height="500" />

6. Place the above variable in the workflow mailer where image should be loaded.