Upon my travels searching for things I might like to do for a major project I happened upon this list by Dani Jones of (funnily enough) things for an illustrator to do.
It includes suggestions such as "create-a-monster-a-day-for-a-month", and smaller activities like "why did the chicken cross the road?".
All of the activities are split into sections such as 'practical projects' or 'academic exercises'.
Dani ( a children's illustrator) also has lots of other content on her site including practical tutorials and even on weekdays a live, streaming show on which she will create illustrations and the like...