There is a font called Kapra and I really like the style it uses in the example images. What would I look up to find more stuff like this?
The font style is geometric and based on rectangles, with strong horizontal and vertical lines.
The image of the dachshund is passive, and highly stylized to mimick old reproduction techniques. Also note the artificial weathering of the background, again to mimick a first-half century look.
This is Constructivism, with strong ties to Socialist Realism. These two art styles have their origins in 1920s Russia, which explains the (historic) link to Poland.
This type of things has it's peak in "dwudziestolecie międzywojenne" (Midwar twenty years). It was heavily influenced by constructivism and modernism. Mieczysław Szczuka, Teresa Żarnower, Jerzy Półtawski who designed first polish font (by all the ł's ą's and ż's you may have idea why we needed special typeface).
Here is a book (in polish) about polish design between 1919 to 1949 http://designteka.pl/nie-gesi-polskie-projektowanie-graficzne.html
In terms of font style, that'd be in the realm of "condensed geometric sans-serifs"
It's not particularly Polish, though it's in the neighborhood, as geometric sans were a big part of the Bauhaus in Germany in the 20s/30s.