So, what you're showing here is that you took the moon and you took the sun and you took everything that seemed like fun... radda radda and such. I kind of wish Nintendo had done more of a yin-yang symbol with these two. They are the opposites and it's a simple yet effective visual. The disc as it is still has a great look overall but it is kind of sterile, too. Your take has more dynamic posing and they are even acknowledging one another. Nintendo just slapped their basic images onto it and shipped it out. A shame.
"Please let me know if this goes against the rules. I'm trying to figure out how to show this the best way possible." - Not sure how it would be. You are crediting your reference material for a piece of art you made yourself. As long as the art is your own, you should be fine.
"I am a huge sucker for orange-blue color combos" - I think the sequel to Super Monkey Ball has that combo, as well. GCN discs just look great in general. I'm a fan of the Namco Museum Collection and Sonic Mega Collection cover art with the bright yellow contrasting the red of one and the blue of the other, but my favorite is still Super Mario Sunshine.
Of the variations you've provided, I greatly prefer the third of the seven. I thought I would love the yellow with red more, but I didn't realize how much I would dislike seeing a red Twila. An odd revelation for me. Heh.