Ok. I've replayed this again.
Wow... did you really swap Willa (in her airship) with a slug? WHY?
The torches in Crystal Fort seem to follow which way you are facing...
I think that the dragon there could be replaced with something like a Rock Monster?
The RR logo on various posts seems to be detached from the post itself... Go sideways to it and you'll see what I mean. Also the crystals (in the first castle) follow you too.
Those sliding things on the top of the castle... What're those for? You don't need to have something moving just because you can.
In the castle at the beginning of the map, there are too many pictures of Chief posing for the same thing. Also, that cauldron could be replaced with a large Slimy Slug head (That's just an idea - if you have a better way to exploit the rolling function, go ahead)
There's too much turquoise in the first castle. I think it should be dark grey and that little band (now yellow) should be turquoise.
The 'crystals on chains' idea doesn't seem to work for me. What's the point of having them there? Can you not just have nothing at the end of the chains?
The 'slimy slug' area has too many holes for it. Having that many holes is never seen anywhere, especially as there are no slugs nearby.
Also, changing Willa's laugh to the slimy slug 'ooh, ooooOOh' noise might work well.
Changing the sky colour to a cavern roof might look nice, 'cause then the pillars would make sense.
The ice textures on the side of the road seem to clash often, with jarring lines as one abrubtly ends and another begins...
The obelisks could be replaced by those ice pillars. Those palm trees (in the original) things.. can you just remove them?
Inside the thingy at the beginning of the race, I've noticed that a) a lot of hieroglyphic stuff still remains, and b) the reinforced solid rock texture is slightly too short so it duplicates the bottom up near the top. This looks awful.
I'm not sure if you could do much about this, but it is fairly blocky inside the thingy and thus this doesn't suit RR walls.
Going inside the first shortcut, something seems to have glitched with the textures at the very beginning of it. Also, the oasis could be replaced by ice.
Still in the shortcut area, those Recharge Seams are cut off half-way and look awful.
Those recoloured tents just don't seem right. Perhaps they could be some rocks, but they're just too angular for RR...
That ice shortcut is great. It's almost a shame to smash it. But having the Sphinx there doesn't really work...
More coming because it's quarter to ten and I should really go to bed...
This might seem like all negative feedback, but this is a great mod. I can see it becoming really good later.