To install Appimages from Appimagehub via CLI use appimage-cli-tool. This allows you to e.g. search appimages with "app search xyz" and install any appimage via command "app install #id".
If you are a developer who is interested to easily build appimages from your code repo, read the guide here.
XSplash is a software project in the Ubuntu community that uses the X Window System to replace the scrolling-text screens that appear while booting a Linux-based computer with a graphical splash screen. Wikipedia