Retro the Video Game History Foundation has released a massive collection of concept art and documents for Sonic 2 (including the infamous Dust Hill mockup)

[Krvavi Abadas]

and here's a link to the documents provided by Tom Payne.

the Dust Hill image, included in Brenda Cook's portfolio. is particularly legendary. as it alongside mockups for Hidden Palace (which would eventually get implemented in a few builds.) were some of the first "screenshots" shown to the public. the post-release interest in what happened to those zones is arguably one of the main factors that led to the game preservation community as we know it today.

(yes, there was actually a little bit of animation tied to it. even though it wouldn't be visible in print.)

 

[batfax]

Incredible how we're STILL finding out new information about Sonic 2's prototypes. Such a shame that none of Brenda's art made it into the final product, since they're all pretty great. Especially love the cactus flower animations.

The associated blogpost also posits the theory that Skychase Zone's original music may've been meant for the snow-themed level and... Yeah, I can hear it.

 

[chocolate_supra]

*muffled squealing*