Here's some news on our work of decoding the usage of sprites.
360 Completed sprites. This is defined by a few things. 1. All of the obvious values are figured out. You can use it any way the game uses it. 2. Most of the more subtle values are figured out, but sometimes, it's just not obvious why a value is set. Instead of ripping our hair out over something that doesn't seem to affect anything, it's marked with No visible change, and skipped. 3. Any unused sprite that clearly does not function in a manner that would let it be used in anyone's level. There are some almost-working but textureless platforms out there, but really, it's not recommended. These are marked as "Incomplete Sprite / Platform" and can essentially be ignored.
100 Incomplete sprites. This is defined as a sprite that is used by Nintendo in their levels, and has values that we don't know what they do. We still have sprites like Cheep Cheeps and Bullet Bill Launchers, and a few more vague things like the Auto-Scrolling Controller, that need a lot of work to make them usable. These are the sprites that we are trying our best to figure out for you guys.
23 Beta / Unused sprites. This is defined by any sprite that is not used in Nintendo's levels that may actually serve a useful purpose.
Possible values have been data-mined and written into both the Incomplete sprites and the Beta sprites. Once Reggie is launched, there should be a spot on a website for folks to help contribute information about the values that are still listed as Unknown.