Content and Merge Field Placement
If the content is placed between a set of merge fields, the merge field criteria must be met in order for the content to populate.
For example, you have an image added to the ereceipt, confirmation email or notification email. The image is placed between a merge field section Pledge Payment.Begin Section and Pledge Payment.End Section. 
The image will only populate if the donation is a pledge. Otherwise, if the donation is not a pledge, the image will not show. 

If you have content that should show regardless of merge fields, it should be placed outside of the beginning and end merge field content. It should not be within the merge fields, unless you only want the content to show if those merge fields apply.

Additional Resources
Specific merge field is not populating in an email message
eReceipts show red X in place of image
eReceipts & Form PDFs are blank when viewed in NetCommunity