Earlier today, Fummy just uploaded a video showing called "VRoid Studio - Viola (The Witch's House) Test" showing off a 3D model of Viola made in Vroid Studio. While I don't think this means anything other than testing, according to the title, I still think it looks nice. (Vroid is a nice free 3D character creator made by Pixiv and surprisingly powerful.) Here's the video:
Also, there are links in the description to the Kindle Edition of The Diary of Ellen, which apparently has a bonus chapter called “A Black Cat’s Monologue” and has a few more illustrations according to Fummy in response to one of the comments of the video.
Here are the links:
Here's some more info from vgperson's blog: