Update for all and another call for help!!
I figured out that subscription is running under service account, so I need to provide <Image access for this account>, not sure how to do this, as I don't have full access to our server.
But this path sounds promising..
Anybody knows what is default service account name for SSRS subscriptions? I can edit report security, but I can't see that account name.
At the same time I see that img got translated into Image_Data in binary format, so I think rdl should be self inclusive..?
Best
Mario