I created this one for a friend's birthday last year, and it was the first time I worked with such a detailed background. Normally, I slack off with the bg of all my artworks, but the structural background was nonetheless fun to work with.
As usual with every artwork, I started off with a clean line-art.
Then I went in and added the colors.
After that, shades and layers of soft glow were added. I added over 20 layers to this piece.
After some minor fixes, it was done!