Here is a suggestion I think could be useful.
Currently Files preview is controlled at the View level.
Suggest be able to control at Field level also.
So, you may omit any of show_preview, image_height, image_width at the View level and include preview instruction at the field.
If at View level you have image_height, image_width but no show_preview, only fields which have show_preview spelled out, will be previewed with View height and width as specified on View.
Show_preview or height and width on field level will OVERRIDE View level preview instructions (if any).