I made a recent visit to the National Gallery in London and was struck by two paintings that weren't liturgical art, but had paintings of liturgical art as details. I took some snaps with my phone (carefully checking with the security guard that I wouldn't be arrested for doing so). 

Some of the figures I can identify, but not all. So here's a question for you: can you identify the figures portrayed? 

Art typically tends to be moved around churches, so unless we have items that are actually fixed and not defaced by the iconoclasts of various times right through to the 1970s -  perhaps frescoes or sculptures - we can't be sure what would have been there in the past. 

I have not seen studies of schemas for liturgical art in the Roman Rite which are as comprehensive and authoritative as those which exist for the Byzantine/Eastern liturgies. I would like to see similarly guidelines developed for the churches of the Western Church and unless anyone can direct me to one, we probably need some research and careful application of thought to develop some for today. 

The first is called the Exhumation of St Hubert and is painted by Flemish artist, Rogier van der Weyden:

Here is the detail of the altar and the art depicted behind it. We see Christ on the cross with Our Lady and St John, with three women and one male saint. I am guessing these are appropriate to this particular church and community. Above there are three small sculpted figures and 12 tiny images - which we can't make out. Then in front of the small reredos, there is what I assume to a tabernacle with Christ in Majesty - after the Resurrection and Ascension - with figures that I presume to be the apostles.

The second is the Presentation in the Temple by an anonymous 15th-century artist:

I find this reredos particularly interesting. It seems to me that what we are looking at is Cain and Abel on the left, and Abraham and Isaac in the center. I am not so sure about the scene on the right. Is it Jacob and Esau, perhaps?

By the way, artists take note, the way to avoid mystification rather than revelation is to tell us in writing who and what we are looking at. Theodore the Studite specified this as necessary in order to make an image worthy of veneration in the 9th century AD so I would always try and put the name of the saints, feast or mystery depicted in writing clearly on the painting itself as a matter of course.