actually I've just noticed that the whole shape tray is greyed out!

Hi Hannah 

Thanks for reaching out in the Lucid Community! To verify are you trying to update your org chart and insert images through the Org Chart menu on the right? Based on what you described it seems like you are trying to update your org chart and insert images using the conventional shapes panel on the right. You can access the Org chart menu by double-clicking anywhere on your org chart – this will open up a panel on the right of the canvas. To insert an image select the employee shape > click the "Layout" tab from the Org Chart menu on the right > click on the "Shape Style" menu. 

To learn more about how to get the most out of our org chart features please review our Org Charts Help Center article. And If I have misunderstood your issue or the steps outlined above do not work for you please send a screenshot of your trouble so I can take a closer look.