I think it's a good idea can choose the size of buttons (not just one, but everyone) in the pop-up menu. Maybe some fixed sizes: "50x50", "100x100", "150x150".
@Mte90 yes, but actually it's not necessary. I mean, if an image (png) is 300x300, you don't lose quality of that one if you reduce the size (you can set the image size: background-size: 100px 100px (or, if i'ts an img: width: 100px; height:100px)) so it's not impossible 😄