It would be nice to have a hand-drawn image/symbol gallery. For example, writing out your own formulas/diagrams and being able to save them at the top of the page in the tool bar (just like how there's a photo option that comes from your camera roll).

Having your own drawn images/formulas etc, would be a lot quicker for the user instead of re-writing out or copying/pasting each time when you need to use a specific shape/image/formula etc.