Ok, so I reviewed the suggestions quickly and…
I’ve tried hiding the imprints with marker pens and crayons (with a prior sail), I tried painting over it (with hand paints and even with spray paint). Of the options, the only one that actually hid the imprint was spray paint, which stiffened the material to the point it became worthless. With everything else the image still showed through.
Maybe if I didn’t hate pirates, or it was some other type of image (like a fishing symbol), this wouldn’t be an issue. Unfortunately, I hate pirates…