Unless it literally downloads them each time on application startup without caching the images locally, they’ve got to be in there somewhere. They almost certainly wouldn’t be embedded in the main executable as resources (which you already checked for anyway), so search for common image types: *.bmp (which it evidently already uses), *.png, *.jpg, *.gif and perhaps even *.tga or *.ani. There’s plenty of other possibilities, but those are all less likely.
With that said… I really wouldn’t recommend running a legitimate (let alone an illegitimate) business on pirated software. Have you at least considered looking at some of the freely available open source solutions?
https://github.com/opensourcepos/opensourcepos perhaps?
There’s a live demo at:
https://demo.opensourcepos.org/
User: admin Password: pointofsale
There’s a fair amount of options: https://www.softwaresuggest.com/blog/free-open-source-pos-software/
Sure. I can see how the relative simplicity would be attractive to you given the use case, and so long as you know how to backup (and restore) whatever it uses for a database, I guess that’s fine. However, if you can’t do basic things like define new products without essentially hacking application assets, well, that’s… significantly less attractive, I would think.
But you’re the one who knows what will serve your needs best, obviously. Personally I wouldn’t want the potential liability of having to use the reporting features of a non-supported unlicensed piece of software when a tax auditor comes calling.