To find the resource folder of the images:
- Right-click or Control-click on the Accordance application icon in a Finder window.
- Select "Show Package Contents"
- Navigate to /Contents/Resources/ where you will see a "watermarks' folder with images 1 thru 130.
- Backup that folder elsewhere to be safe.
- Quit Accordance and have fun editing the images.
You can download a set of updated images that you see in this post. They add a consistent bluish-greyish color theme on top of Accordance's default images. You can install them by dragging the icons into the watermarks folder you navigated to. The images are available here.