I love it all.
The shae of the red, giving garnets body a sorta...galaxy look. Makes her seem like the being Eternity from Marvel. Who is the living Manifestation of every living creature in the universes mind. And Garnet, is the manifestation of those twos love. I mean, she's that ALL the time. They love each other so much, that they did this since I guess Gems don't have marriage.
So, a fusion was the best way they could think of to be together, have a commitment and show their love. Thus, they are literally the HEART of Garnet. And that you've drawn that, this, just makes my heart soar. The imagery, the beauty and emotion in this pic. Leave me breathless