At Manufaktura pottery (at Gdańska street) you can paint your own pot and visit the factory to get the full experience of making ceramics wares. The place is fully, professionally and tasty adapted for those purposes and they also have a tea/ coffee/beverages/ cake shop and WC (check out the pottery sinks and attachments).
At the workshop you get a plane piece of biscuit pottery which you can paint (with brush and stamps) in any color and pattern by your unique design. The factory fires it for you later and I can take care of the shipment (link). You can also leave your purchases there for shipment.
While the 20 minutes' tour you get to know all the stages of making Polish Pottery- molding, shaping, drying, cleaning, 1st firing, painting with traditional sponge stamp method and paint brush, glazing and final firing. VERY worth doing. Get more info at www.ceramiczna-przygoda.com.pl