If you go into the Member's Area you will find a page called "Staging Area". This is where I can bounce ideas off members of the Committee before they are formally published. Permissions for the Staging Area to view have only been given to the local site administrators (made up of the Committee).
I have now loaded the Staging Area with 3 slider includelets 4x3, 16x9 and natural aspect image ratios (each specifically marked). In each slider I have inserted the same photograph and the same logo image to demonstrate how each performs. The one that best meets my needs is the Natural Aspect Ratio, the problem is that the photo image is too large and there doesn't appear anyway of resizing it.
Under the sliders I have inserted the same photo and image from the Asset Library (without changes) and then a second time in which I demonstrate the abiliity to decrease of increase the photo/image.
The Staging Page has not been published as the Committee would wonder what I was doing, but you can see the effect by using the Preview facility.
I hope that this helps. Can you also let me know when you have viewed the page and I can wipe it clean.