I have an images folder.
When I push the post to GitHub Pages some images don’t show while others do?
The image names are correct and the paths are the same?
Hah! Excellent catch @fabiomux! I tried a few upper/lower case variants, but never thought to tweak the extension.
It looks like the OP is using a file system browser that hides the extensions, so the problem is invisible on their local system. They may also be using a case-insensitive file-system (macOS and maybe Windows), so the site would run fine locally, but fail when uploaded to a case-sensitive file-system (i.e. Github Pages).
Thank you @chuckhoupt, yes it is the Windows file manager in the screenshot above and it hides extensions by default, some applications under Windows assign an extension in the upper case format, probably some DOS heritage…
Possibly the difference is due to some editing or conversion step (e.g. screen-shot software, or editing software used to crop or convert an image). As @fabiomux mentioned, older software may default to uppercase extensions for compatibility with ancient Microsoft OSes.
You should be able to just rename the files to use consistent case for the extensions.