This picture was taken immediately before Benediction of the Most Blessed Sacrament about 4:00PM Divine Mercy Sunday at the end of our Divine Mercy Holy Hour, the third Holy Hour of the day in the parish.
We displaced, as it were, the Divine Mercy painting for emphasis. One priest I know, who hates the Divine Mercy, says that this painting is the worst thing ever in the history of art as it “blashemously” does not depict the Sacred Heart, just rays of light representing the blood and water which gushed from Jesus’ Heart when pierced through with the soldier’s gladius:
Anyway, that picture of Roman gladii is by Matthias Kabel on Wikipedia’s “Gladius.” Such swords were so heavy they could cut someone in half with one hit, so wide that the wound was at least as wide as a man’s hand. When Thomas put his hand into the side of Jesus he surely touched that Heart pierced through.
Anyway, yet another priest, a good friend, who loves the Divine Mercy, told me that Jesus told Saint Margaret Mary that His Heart is not to be depicted without the rest of the human nature of the Divine Person, such as with this image in the Major Papal Basilica of Santa Maria Maggiore in Rome (on the epistle side of the Basilica):
This topic of the depiction of the Heart without the Body came up because I’m thinking of having a mosaic created for the front of the altar with the Two Hearts, something like this:
I would switch the places, left to right and vice versa with the two, and slightly overlap them, perhaps all told some 18″ wide.
My answer to the objection that the Sacred Heart is not to be depicted apart from the Body was the infant Jesus at the Shrine of the Most Blessed Sacrament:
But my priest friend said this was all good because, although apart from the chest, was with Jesus.
My response to was that my planned mosaic was all good because the Body, Blood, Soul and Divinity of Jesus, the Most Blessed Sacrament of the Holy Sacrifice of the Mass, and in the Tabernacle, is absolutely present fully. :-)
Anyway, I’m wondering if any reader knows where it is that an account of Jesus giving such instructions to Saint Margaret Mary Alacoque is to be found.
ARISE! LET US BE GOING! 
Happy Easter Father!!
In this second great revelation, Our Lord began to unfold His intentions and to formulate His promises. The image of the Sacred Heart of Jesus is the symbol of His ardent love for us. This image was to be exhibited in homes or worn on the breast, especially in the form of a medal, offering promises of graces and blessing to all who would venerate it. But for the moment, Margaret could not reveal anything of what she had seen, because the time had not come to do so. These revelations would first have to endure trial and suffer great opposition. And there was a lot more that Jesus desired to reveal. https://www.piercedhearts.org/theology_heart/life_saints/margaret_mary.htm
Lots to read on this link, could not find instructions you mentioned. Actually the heart is depicted on Its own, no body, as you scroll on the site. As to the Divine Mercy painting, where are the rays going to come from if not His heart? The painting is stressing His mercy, of course the Sacred Heart is understood!!!
Father, your idea of a mosaic of the Sacred Heart of Jesus (on the left) and the Sorrowful and Immaculate Heart of Mary (on the right), somewhat overlapping, is beautiful and would be in tune with what God wanted clarified with the Miraculous Medal given to Catherine Laboure in 1830 and the vision of those two hearts “adhering” (overlapping somewhat) shown to Berthe Petit about 80 years later. During Midnight Mass she saw Our Lord’s wounded Heart with that of His Mother pierced by a sword, and so close they appeared adhering (partially overlapping / fused / united). Then she heard Our Lord: “Cause My Mother’s Heart transfixed by the sorrows that rent Mine to be loved’.” The vision was repeated some weeks later but this time with the Holy Sprit, in the form of a dove, hovering over the adhering Hearts, rays of light emanating from Him toward them. Again she heard Our Lord speak: “You must think of My Mother’s Heart as you think of Mine; live in this Heart as you seek to live in Mine; give yourself to this Heart as you give yourself to Mine. You must spread the love of this Heart so wholly united to Mine.”
Perfect, Aussie Mum.