Hi inukaze,
I have create my own .AppImage for my software following this step-per-step tutorial that I recommand it for you:
How to create an AppImage to bundle your software
Thanks @flaxalex57. Just keep in mind that in order for appimagetool to produce a good AppImage, you need to have a good AppDir where all dependencies have been deployed properly to begin with. This can be quite some work to do properly. So instead of using the low-level appimagetool you may be better off using one of the higher-level tools that are dedicated to doing this.
You can find many such tools for various programming languages and evironments at