Separate to darkened item frames but possibly related, upgrading from previous version deletes some item frames and their contents.
The picture shows an example of how both issues occur, darkened on left, deleted on right.
MC-103083
Upgrading from previous 1.9 version deletes some item frames
Resolved
Duplicate
0
Dale Allanson
(Unassigned)
Unconfirmed
Minecraft 1.10 Pre-Release 1
Retrieved
Not sure about the missing item frame part, but regarding the blackened part, it's a duplicate of MC-102894. Missing item frame part could be caused by MC-65040. I also found a thread that could also be a duplicate MC-102958.
I'm just going to say that this report is a duplicate of MC-102958 and MC-102894.