Ah, it's good to find this thread, migrated from SA. I'm in the process of compiling some information and pairing down my duplicates and have been on the lookout for a copy of that RotD promo copy, but obviously, not as intently as others
I've picked up all of the LRG reprints, however, I haven't opened any of them yet to see if there is any difference in the disc contents.
I have discovered different night trap discs, which may or may not be related to the MA-17 cardboard variant from the original Sega CD branding and a third for the Digital Pictures reprint later. I discovered them separated from any boxes.
There was also a LaserActive music sampler, but I'm not sure if that strictly counts as a Sega CD item.
I also have two discs which claim to be Power Cuts 1, each with different tracks. One came in a normal jewel case, the other with a cardboard sleeve (that was cut to bits by the time it reached me.
I'm (slowly) compiling a lot of Sega CD info, so I'll probably have more to post as time goes on.
Thanks again @final fight cd. Your original thread on SA helped a ton.