The image must be web accessible. Previously I use an image from HA but since i move to bearer token and no longer use HA Password my HA links not accessible so for now I use link to motioneye images.
action type: call service
service: my html5 notification service
service data:
data:
image: >-
https://motioneye.com/picture/5/current/?_username=thisguy&_signature=lottanumbers
renotify: 1
tag: alert
timestamp: '%m'
url: 'https://myHAsite.com'
vibrate: '700, 100, 700'
message: '{{ as_timestamp(now()) | timestamp_custom(''%H:%M'', true) }}'
title: GATE Open