Running through the command line doesn't seem to raise any error messages, but here's the first image I experienced the issue with. After loading it in and changing any of the sliders it will crash. Like i said, I was just messing around with random images to see what they would look like, so this isn't a realistic use case. I figured some people might want to use the software with very high resolution sprites, so I thought you might want to pick up and fix the issue, but I suppose if you only intended the software for small images it's no big deal. Either way, it doesn't affect me directly lol. 
I also did test it with a few other generic texture images (like wood and stone textures you would use in 3D software), and found that loading more than three 1024x1024 textures would crash it. Here's an example of one of the images I used.
Once again, if this is outside of the use you intended for the software, it's no big deal, just though I'd let you know :D
I'm using windows 10 with 8GB of ram and 7th gen i5, so i don't think it's a problem with my hardware. Perhaps there's a problem with memory allocation in windows?