We won’t do the planning for you. Ask this an you get 100 different suggestions. We won’t do the planning for you. But happy to help with more specific questions.

There are about 200.000 km of railways in Europe, with more than 36000 stations to potentially go to. Almost all of them doable with a Eurail pass.

Take a map, and see where you can and want to go to. Use a reliable planner like www.bahn.com and check where you want to go to.

We also advice to read an intro into European train travel, like this wonderful website: https://www.seat61.com/european-train-travel.htm