Mutations and monsters to Chesty's icons

Quick question here. I’ve been working on a custom mutation branch, complete with source code sorcerery, and some monsters/badguys to go with it. I’m hoping to chain the mutations to icon changes in the windows graphical version of the latest experimental, but I haven’t the slightest clue how to pull that off.

Does anyone here know how to make your mod’s items, mutations, and monsters show up in the game with tileset assets?