how to remove back cover and waveform cover?

Hi! How to remove back picture and waveform picture? field "picture" and "cover" erasing all images from mp3 files... how to remove 1, 2 or 3 picture?

If you have a set of files with the same set of covers you can either use the tag-panel and its display or the extended tags dialogue.
In the tag-panel right-click on the incriminating picture and select "Delete cover".
Repeat until all unwanted pictures have been deleted.
Press Ctrl-S to save the changes.

In the extended tags dialogue you can press the red x for "delete" next to the display of the picture to delete it.
"OK" then saves the changes.