Did you use the Insert Menu to add this graphic to your layout?
Did you perhaps select the "by reference" option?
If so, re-insert the image without this option selected or just copy/paste the image to your layout.
Thank you for advice, Phil.
I used way I expected is ready for this purposes: in Inspector > Appearance > Graphic I used Image as Fill and then I selected PNG and JPEG image. There is no checkbox I can select reference or not, I expected the file is used correctly.
Copy & Paste seems to be not only easiest way, but reliable too. :)
Does that mean that copy/paste worked when using the inspector did not?
This might be a bug to report over in Report an Issue. If you choose to do that, you can paste a link to this thread into your report to save typing.
Sorry to jump in on your thread, but I think I'm experiencing the same issue - background images are displayed on an internal connection, but not on an external one.
After a bit of poking around on the external connection, I can see that WebDirect is attempting to load the theme images using the internal IP of the server rather than the external address.
E.g. trying to load an image from http://10.0.2.218/Streaming/MainDB/FM-3A9B94B5-3C33-6C4E-8D89-1AFAE7873DBC.png which works when I'm inside my corporate network but, externally, that address should be something like https://fmserver.mycompany.com/Streaming/MainDB/FM-3A9B94B5-3C33-6C4E-8D89-1AFAE7873DBC.png
I'm afraid I don't know how to fix it... I ended up here while searching for a solution, but I'd be interested to know if your problem is similar.
Sounds like you may have encountered this known issue: Contents streaming to internet is impossible over IWP
This is one of many acknowledged bugs that can be found in the Known Bug List thread here in the Report an Issue section of the forum.
It can also be downloaded as a database file from: https://www.dropbox.com/s/jt09b82i0xijbu3/FMP%20Bugs.zip