I Found some screenshots, even the early JCS.
Yeah, this is the very first website of JJ2 ever.

Ooh, that's the MLLE screenshots right there!

Also, I must say their news posts are worth reading! There are news posts like:

Arjan is going nuts and coding his brains out. He put in a type of switch block in the game similar to the mario games. You destroy the appropriate metal crate, and blocks either appear or vanish. It creates a lot of cool puzzle ideas, most of which I'm putting into a lot of levels!

Imagine this was posted while he was programming the Trigger Scenery event for us! Y'know, the thing that made a lot of extra custom gamemodes possible (GroundForce, TeamBattle, Jailbreak, etc.) He couldn't possibly have imagined it would be so much more than just "a type of switch block similar to the mario games"!

EDIT: Oh wow, the even have an MLLE page.

The background of the beach level makes me curious. It's different. Is there a higher res version of it? Is it still possible to acheive currently?

Looks like some trying to play the beach level in the lowest res and it failed. Really I Want these Alphas

Never seen this website before, I only heard of it's name from Jazz2City.

Looks like Bill was quite a dedicated JJ2-reporter back when the game was in development.

I Found the link on a Noob Clan's website. WTF