Ok, Does the default image include a small watch "waiting for approval" also in your case ?
There seems to be a... bug :silly: for images approvals within the Field Groups.
If you turn off Image approval in the CB configuration / Moderation tab, or
If you turn off Image approval in the image field settings, in Parameters / Image limits / Approval setting,
then the image displays fine in the Field Group.
If not, then (bug), it doesn't appear in the regular image approvals view nor in the CB Workflow module.
I have added a bug tracker item #8087 for further bug investigation:
forge.joomlapolis.com/issues/8087
In the mean time, switch to No the Approval setting for that image field, and newly uploaded images should display (already uploaded ones will stay in the waiting for approval mode).