"Album artwork" area is to small, people can't see the detail. This problem can be solved with additional split bar between buttons (and album artwork) column and fields area. With that bar, people can resize column width. The buttons no need to adjust its width, but the album artwork does.
You can double click on the album artwork preview (or select the "Picture" frame and click the "Edit..." button) to open the dialog to edit picture frames. There is a "View" button, which lets you see the picture in its full size.
I think it is tedious if we do more action (moreover entering edit mode), just to see a slightly larger image. The preview is already in there, why don't we just enlage a little. There is time when we use it not for edit the metadata. In my case, i use it to cover the limitation of file manager (like Windows Explorer). My real intention is to open a particular file with my prefered app (by means looking at the preview and maybe other metadata first).