I'm not known for music hacks, but I recently heard some music that sounded quite amazing. The YouTube member, BowieZ (http://www.youtube.com/user/BowieZ), has had a knack for making game music, even if it's for fan-made stuff. Some of his work was actually quite entertaining to hear.
Anyway, I did submit a BRSTM of one of his compositions onto Brawl Vault. Namely, Rainbow Planet.
Normal: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=9414&DiplayName=Rainbow%20Planet (http://forums.kc-mm.com/Gallery/BrawlView.php?Number=9414&DiplayName=Rainbow%20Planet)
Fast: http://forums.kc-mm.com/Gallery/BrawlView.php?Number=9415&DiplayName=Rainbow%20Planet%20(Final%20Lap) (http://forums.kc-mm.com/Gallery/BrawlView.php?Number=9415&DiplayName=Rainbow%20Planet%20(Final%20Lap))
Previewhttps://www.youtube.com/watch?v=UUpXW1LdxPMThe songs are looped, but I never tested them out in-game. They're also best used with most Super Mario Galaxy themed hacks.
Edit: I tested out the BRSTM, via Riivolution, and it works rather well. The volume level of the music is slightly louder than most default tracks though.
I love this guy's music. He should work for Nintendo.
This would fit perfectly with your Galaxy Road texture for Mario Circuit.