Originally Posted by
Xanthorrhoeas
You need a tough, water-resistant or waterproof finish.
About 30 years ago my wife (an artist) hand painted scenes & still-lifes from our house on hardboard place mats and then also made some with glued-on paper cut out of some of her other artworks. We finished those with a clear gloss oil-based polyurethane (Estapol brand but others are equivalent) and they have served us well for many years. Some are beginning to peel and show signs of age but they have done well in my opinion.
Today there are plenty of options including water clean-up polyurethanes in a range of gloss levels.