I'm gonna present in short the greatest Poles so that you know who they are. I'll also add some ideas about the look of the stamps :)

Fryderyk Chopin

He was a Polish composer and virtuoso pianist of the Romantic period who wrote primarily for solo piano. He has maintained worldwide renown as a leading musician of his era, one whose "poetic genius was based on a professional technique that was without equal in his generation.

https://static-files.nifc.pl/_foto/osoby/1/700951_1623316672.jpg - add some musical notes next to his face :)

Mikołaj Kopernik

He was a Polish astronomer who proposed his theory that the planets revolved around the sun (heliocentric theory) in the 1500s, when most people believed that Earth was the center of the universe. It formed a strong foundation for future scientists, such as Galileo, to build on and improve humanity's understanding of the motion of heavenly bodies.

https://static.polityka.pl/_resource/res/path/e3/23/e323fa4f-3172-4527-9227-d563f1387e1d_f1400x900 - the stamp could have Kopernik's face and the sky with stars behind him or sth like that

Maria Skłodowska-Curie

Maria Skłodowska-Curie was a Polish physicist and chemist, she was the first woman to win a Nobel Prize, the first person and the only woman to win the Nobel Prize twice, and the only person to win the Nobel Prize in two scientific fields. She discovered 2 chemical elements: polonium (which she named after Poland) and radium. If you do create a stamp with her, do remember to write her name correctly (Marie Curie is INCORRECT!). It's MARIA SKŁODOWSKA – CURIE

https://s.ciekawostkihistoryczne.pl/uploads/2014/07/marie_curie.jpg - although it's not her in the picture - it would be nice if on a stamp she held a test tube or other scientific dish

https://bi.im-g.pl/im/f3/d2/19/z27076339ICR,Maria-Sklodowska-Curie.jpg - this is her

Jan Paweł II – John Paul II (Karol Wojtyła)

He was the head of the Roman Catholic Church (pope). He was he first non-Italian pope in 455 years and the first from a Slavic country. His pontificate of more than 26 years was the third longest in history. As part of his effort to promote greater understanding between nations and between religions, he undertook numerous trips abroad, traveling far greater distances than had all other popes combined. His unabashed Polish nationalism and his emphasis on nonviolent political activism aided the Solidarity movement in communist Poland in the 1980s and ultimately contributed to the peaceful dissolution of the Soviet Union in 1991.

https://i.iplsc.com/-/000A4I4XV8J0CT2S-C411.jpg - I think this is a perfect reference pic. You can add for example, a halo over his head because he was declared saint after his death.

Andrzej Wajda

He was a Polish theatre and film director. He is considered one of the world's most renowned filmmakers whose works chronicled his native country's political and social evolution and dealt with the myths of Polish national identity offering insightful analyses of the universal element of the Polish experience – the struggle to maintain dignity under the most trying circumstances. He received a Honorary Oscar.

https://mnk.pl/images/upload/wystawy/czasowe/2019/Wajda/wajda2_detail.jpg - you can try portaying him with a camera or movie equipment, or with an Oscar award

Lech Wałęsa

is a Polish politician a Nobel Peace Prize laureate, who served as the President of Poland between 1990 and 1995. He was the first democratically elected President of Poland since 1926 and the first-ever Polish President elected in popular vote. Before that Wałęsa became the leader of the Solidarity movement, and led a successful pro-democratic effort which in 1989 ended the Communist rule in Poland and ushered in the end of the Cold War.

https://bi.im-g.pl/im/5a/c6/12/z19686490V,Lech-Walesa-w-maju-1989-roku.jpg - here's him showing the v sign, you could use that and add the colours of a Polish flag behind.

Adam Mickiewicz

was a Polish poet, dramatist, essayist, publicist, translator and political activist. A principal figure in Polish Romanticism. He is widely regarded as Poland's greatest poet. He is also considered one of the greatest Slavic and European poets and has been dubbed a "Slavic bard". A leading Romantic dramatist, he has been compared in Poland and Europe to Byron and Goethe.