[Feature Request] Background image ideal resolution value while editing dashboards

[gnalbandian]

Hi.

It would be nice to have, while editing dashboards, the ideal resolution for an image if we would use the backgoud image option.

Sometimes I spend lot of time resizing images just to get it look right in some of the widgets background. Sometimes it looks strech or compress.

Having a something like the image below would be nice.
I am not sure if possible, since resolution should be calculated depending on the device running the dashboard. Maybe the image ratio (4:3, 16:9, etc) would be a better idea.
Let me know what you think, and if there is a simple way to know the ideal resolution for a widget box without too much hustle