I am not yet of a mind how to include Our Lady's Immaculate Heart. I would like to, as it is intimately connected to the Sacred Heart, but there is a question of aesthetics, will it look right? Let's see if I get some inspiration! Such symbols don't usually appear in classical Byzantine iconography.
When Jesus is shown enthroned in Glory, He is usually flanked by Our Lady and St John the Baptist, who represent the New and Old dispensations. John bears witness as the last of the prophets to Jesus, the Lamb of God who takes away the sins of the world, which takes us to the very centre of what it means for us to encounter God's love as known in Jesus.
You will notice that I have done some more work on the red nimbus, adding a darker centre. Without this the shape was too dominant, overshadowing the figure of Jesus rather than drawing our eye to Him and His Sacred Heart. The heart isn't finished yet, and will be worked on further. However, so far I have been working to develop a sense of illumination and transparency.