No, its all up to you-though if you google or are apt with apps or blogs there will certainly appear a few dozen suggestions. Most juniors seem to want to do the capital shuffle: visit as many capitals as can do-33 countries participate in pass and you can probably do a new one every day-but I dont think that is the best way to spend it.

You choose for how many days on the train you like to do-price is higher as more days wanted-and DO, DO be aware that the routes that #2 newbees all seem to want to do-racing on hispeed via Fr to sunny ESpana is full of rocks: ALL trains via this route need REServ-hard to get and add a lot to expense.

done such trips several times
It all depends on you which cities/places you visit and what you wanna do. There is no general answer :)
You may start with writing a list which places you wanna visit
Step 2 check the trainconnections and bring them in a logical order
Step 3 adapt your list until it fits your Holidays.

My general advice try to avoid Spain due the Reservations sameapplies for France & Italy but here you can come arround with Intercity´s and Regionaltrains

A “beginner” tour for City explorer is Brussels - Amsterdam - (Hamburg) - Berlin - (Dresden) - Prague - Vienna/Bratislava - Budapest - Croatia - Slovenia - Italy.
You can catch from Berlin trains to Poland aswell
and ofcourse explore many more Cities in the Countries the route above is just one suggestion of the million Interrailcombinations that are possible :D

You may search what the Interrail & Eurail Packages and tour operator offer and then create based on their offers a own route. As these “Packages” and tours are often overpriced.

https://www.interrail.eu/en/plan-your-trip/last-minute-no-reservation-trips
Interrail even offer a own website with suggestions