No sphere, just some blurred white circles and brushed clouds. Then I did the composition with the model and floor. Its probably my fav part actually. The colors and how they blend with the model and subtle way it looks.
What a beautiful and organic model! I love the structure with the heart in its centre, that reminds me of an scifi artefact. The shading is simply brilliant as well as the gradient from the structure to its base. Very well done and a wonderful gift!