Well, the initial idea was to have a master theme with three variants: Blue, Space & Candy.

Intended features:
 - Background animations!
 - Simple palette; the simplicity would allow you to change all colors on one screen, in the admin Current Theme panel... NO NEED TO EDIT CSS... 
 - Auto-generated SVG banner
 - The colors you choose under "Current Theme" are automatically reflected in SVGs, e.g., the banner & hamburger, etc. (no css or photoshop edits...)
 - The colors you choose under "Current Theme" are automatically reflected in the editor (no css edits...)

My favorite feature:
 - Radio buttons & checkboxes use your selected colors...  They're not all the browser white & blue defaults...  (See the background on the checkboxes for the Starflight search form, below.)

This morphed into 3 themes: Starflight, Blue Mood, & Cotton Candy. 

Starflight has been approved, and may be downloaded here:
https://custom.simplemachines.org/index.php?theme=3007

Note I use GitHub for everything, and my Cotton Candy & Blue Mood submissions may be previewed here (these are not yet approved by SMF):
https://github.com/sbulen/SMF-Cotton-Candy-Theme/releases
https://github.com/sbulen/SMF-Blue-Mood-Theme/releases

Download the .zips named after the theme & they install like any theme. 

Enjoy!

I figured I'd share Drake's thoughts on the default browser backgrounds/foregrounds for checkboxes!

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They look really good and the features seem real nice. Good work for sure.