Docwiki says that there is a 100mb for iblite but there is not a limit for ibtogo.
https://docwiki.embarcadero.com/RADStudio/Alexandria/en/InterBase_ToGo
Anyway for desktop ibtogo has cost. For mobile it's a free deployment if you have Rad Studio enterprise.
Iblite is free, but restricted.
Maybe you can contact Embarcadero and look if they thought about using ibtogo for free for demo purposes provided you bring business when you sell your app.
Otherwise you may use iblite for demo systems storing the images as files and only the path to them in db... not ideal but free...
Good luck