Failed to load mods: The given sprite rectangle (left_top=0x0, right_bottom=820x820) is outside the actual sprite size (left_top=0x0, right_bottom=144x144).
See the log file for more information.: ElectricHeatingTower/thumbnail.png

500x500 is what recommended. as of what I've heard.

Roger, will fix. edit Fixed in 0.3.2. I'm genuinely not sure why this even happened. Far as I'm aware, there are not settings for thumbnail size, so I don't know why the game insisted it be 800x800. I did resize the thumbnail on last release, so that's what caused it, but I'm not sure WHY.

thumbnail.png — Thumbnail to be shown on the mod portal and in the mod browser in-game. Ideally a 144x144px image file.

src: https://lua-api.factorio.com/latest/auxiliary/mod-structure.html

So here's what happened: I didn't create this mod. I commented on possible improvements and was unceremoniously handed admin access to it. I did a few changes and mod settings and such. When updating the mod to 2.1, I resized the thumbnail to 144x144, which seemed to cause a crash for Sgamez. I don't know why, so I did the only thing I could and reverted the thumbnail to the original author's file.

I tested 0.3.1 and it works fine for me, no error messages, no crashes.
Seems to be something else, maybe another mod conflicting with this one.
Factorio stable 2.1.23 win x64

Worked fine for me, as well. Guess I figured it was an easy and cheap fix...