You can do as prod said or alternatively decide to keep the album art images in the library and simply configure your standard image views to not show those images.
You can create an additional view that shows only the album art images and even views that show the audio files and album art together. I use that possibility extensively.
You can edit any library view by adding inclusion or exclusion rules: select the view in the tree > right-click > Customize View > Options > Advanced > Set rules for file display...
I just posted a list of my replies that answer various cover art questions and also explain how I use cover art beyond the usual, basic album art system. It is
here (and continues in the next reply in that thread). Be prepared that there are lots of reading and not all of it may be useful for you.
EDIT
If you just want to remove the album art images from the library you can use the search feature for finding them. For instance, you can first open an image view and then type the path to the base folder in the search box.