Currently, It's a PITA to add a background image to a chart. IIRC,it would be awesome to add a UI option to add your own background image to a chart.
Steps to reproduce:
1. Create a new spreadsheet with some data. Create a diagram.
2. Right-click on the diagram, select ''Format wall''.
3. Click the Area tab, select ''Picture''.
4. Find that you have no easy way to add your own image (''Browse'' button to add your own image / file path).
No browse button to insert your own background image by file path.
Add browse button to add your own background image as a diagram background.
Platform (if different from the browser):
Browser: Mozilla/5.0 (X11; Linux x86_64) AppleWebKit/536.5 (KHTML, like Gecko) Chrome/19.0.1084.56 Safari/536.5
I think this would be a nice feature.
Seems to be fixed in master and most likely some older builds.