AppImages often come with the .desktop files and icon assets embedded in the squashfs filesystem.
- Unpack the AppImage:
[application].AppImage --appimage-extract, note: you can see other appimage options with--appimage-help - Find the relevant files and copy them:
# Copy the .desktop file from the squashfs-root to the .desktop file store in ~/.local/share/applications/
find squashfs-root/ | grep .desktop
cp [desktop_file] ~/.local/share/[desktop_file]
# Copy icons to /usr/share/icons
sudo cp -r squashfs-root/usr/share/icons/* /usr/share/icons/