This will be covering all the entity types and individual entities we see in Kane Pixels Backrooms

SL - Still Life

Still Lives are the complex’s re-creations of living beings, some still lives are more developed than others but they seem to be anatomically completely different than normal living beings. The respiratory and pulmonary tracts are not fully developed for most of them. They seem to be made up of a sponge-like material, even their bones are tiny intervowen bits instead of a single solid bone

LF - Lifeforms

Lifeforms, as classified by Async are theorized to be a modified pseudomonas flourescens or Hay Bascilus (more likely)

Some speculate they have Still-Life like origins aswell

U - Unknown