Javascript - Learner Name/Avatar

You chose the right word - reference. For the name, use a text input box, and when you want to use it, insert a reference to that variable into a text box.

For the avatar, store their preference in a variable, and use it in the condition part of a trigger.  e.g. Show avatar Fred when timeline starts on this slide if avatarChosen = fred

Of course, you would need a trigger for each of the choices of avatar that they have. If you use it at the same time on every page (like at the beginning of the slide), you might explore putting the triggers on a master layout.