Ability to set background width type not available (All images crop)

When a background is too large,  it simply crops it.  

I can not find any ability to set it to anything but width 100%.  Being able to set a width/height would be great.  But even selecting a css fill type would suffice:

Background fill type: native, fill, contain

I looked at fabric and there are options for changing the backgrounds but nothing exposed. 

Love the tool.  Thanks.