A possible term is 'counterchange pattern':
"Patterning in which a dark motif on a light ground alternates with the same motif [in] light on a dark ground." (lexico.com)
The Frisian artist M.C. Escher famously made extensive use of this type of pattern, inventing a lot of new ones.
Take a look at his work Metamorphosis III from 1967-68, for example, which contains many patterns of this type, all organically transforming into one another:
As you can see, they are not all counterchange patterns: often Escher's patterns involve two distinct units, being not only visually but also symbolically inverted (e.g. angels and devils).
For more examples, see this page.
A broader term that incorporates both types of patterning is tesselation:
"An arrangement of shapes closely fitted together, especially of polygons in a repeated pattern without gaps or overlapping." (lexico.com)
Also check out eschersket.ch if you're interested in creating repeating patterns yourself.