Based on the name itself:
* Ryszard: This is the direct Polish translation of Richard and could be used as a nickname.
* Rysio: This is a common nickname for Ryszard.
* Rychu: This is a more informal and friendly nickname for Ryszard.
Other possibilities:
* Richie: This is an English nickname that could be used in Polish.
* Rick: Another English nickname that could be used.
Ultimately, the best nickname for Richard in Polish depends on the individual and the context. You could choose a nickname based on their personality, their preferences, or simply what sounds best to you.