Remove gallery button and image size

[paolosax]

Hello
Great plugin - I'm testing it and I wonder if there is a way to implement a "remove" button to the customizer gallery (since now looks like it is only possible to modify, leaving at least one image).

Also, is it possible to set the image size passing a custom thumbnail size? I've tried the solution posted at https://make.xwp.co/2016/08/12/image-gallery-control-for-the-customizer/ but I can't get it to work.