Hi, I've just started playing and some of the images seem to not be showing up in the game whereas others are fine. Is this what you meant by "placeholder art" or is it a bug? 

Hi, this looks like a bug, if you can, please either reach out on my discord so I can investigate or use inspect element feature, click "console" and let me know what errors are showing up there. From just this screenshot it would appear to me that the images were not exported correctly but it's very hard to tell off one image. Also let me know if you're playing the web version or a locally downloaded copy, and which internet browser you launched the game in.