We tested a donation form with the option to send an eCard and the eCard image does not display when it is received.
To resolve this issue, please check the image link within your eCard stationery. Ensure that the link you are using to pull the image into your stationery is an absolute link rather than a relative link. See Relative URLs versus Absolute URLs for more information about the differences.
Example of a relative link that won't work for eCard images to dispaly in email clients:
Example of an aboslute link that will work for eCard images to display in email clients: