When you Download a chart as Image (png), by default the Resolution is set to 96 dpi. If you make the chart to full screen (Or any size) and download, even then the resolution remains at 96 dpi ('Current' mode). Due to this, images downloaded at full screen size, show some issues like the axis labels are shown in smaller font or legends move to corners or blurred images etc. It would be helpful to get high resolution images for the Business users if the Resolution is automatically changed/suggested based on the size (Width x height) and type (png vs jpeg) of the image.
I understand there is a 'Custom' option for the users to change/increase the resolution to the desired levels, however what we have observed is that, many of the users just export with the 'Current' option and end up with low resolution images.