"Everyone can paint" used to be the name of a Dutch toy set when I was a child.
With really basic drawing skills it is possible to make useful "iconic" charts. The umbrella below was used to highlight how a strategy has shielded one of my clients from the full effect of the 2008 economic meltdown.
Look at shapes and see how they are decomposed in very simple elements: a few ellipses and some rectangles. On the right I gave them a different color to make them visible. Make sure that everything is neatly spaced out and symmetrical. The background image was purchased on iStockPhoto.
The key lesson: simple drawings do not have to look simplistic.