I did a little more on the Mithras pages. I was able to identify one of the images that I found online and create a CIMRM page for it. The section in CIMRM on material from Alba Iulia is not very easy to work with, and I was reduced to looking through the limited number of illustrations in the same volume, just to find out which relief I was looking at. There must have been several Mithraea at Alba Iulia, judging from the number of reliefs of Mithras killing the bull; yet none are mentioned in the CIMRM. One was discovered in 2010. There must have been others.
Still, it is impossible for a single amateur like myself to do more than scratch the surface of Mithraic archaeology. I console myself by thinking that what I do is at least useful, as far as it goes.