The picture looks like they are serving on the Bier. The Russians do not have a canopy over the tomb like we do. If I tried to serve a Liturgy on the Bier, I know that I would hit my head. Besides, as I mentioned earlier, in Antiochian practice the Epitaphios is placed on the Holy Table after the procession at the end of the Lamentations Service and stays there until Ascension.
It's an interesting practice.
In our tradition, we don't have an Epitaphios on Good Friday. We bring out a cross and after a lengthy office, we offer incense before it, prostrate before it, elevate it as on 14 Sept, process with it, and then we "bury" it: we wash it, anoint it with oils, spices, perfumes, wrap it in linen, and "bury" it in a particular way (the rubrics refer to the example of the prophet Ezekiel in Ez 4.4-8), usually in a special compartment under the altar. Then the "tomb" is sealed and lamps are kept burning before it.
Until Pascha, when the cross is "resurrected", that altar cannot be used for anything (the original tomb, after all, was sealed and guarded to prevent tampering), so the Saturday Liturgy must be served at a side altar (if present), or else an altar must be set up outside the sanctuary in the nave. The idea of serving the Liturgy on the tomb just doesn't work liturgically for us.
If you don't mind getting a stiff neck, you can see some of these rites beginning here