It makes a change to find someone with an interesting itinerary! It’s only a personal opinion but I think Dresden is worth a visit and then I would make my way over to Koblenz (DE) and travel back up to Rotterdam (avoiding the High Speed Line) via Cologne. The smaller towns on the Rhine are lovely to visit. If you can afford it avoid the night trains and stay in an hotel or hostel. Then you don’t miss the scenery and even in a sleeping car you won’t be well rested for a day of sightseeing. Read all the sections about reservations. AnnaB has a comprehensive post about using the pass.
Well on the planned route there aren’t really suitable nighttrains available in my opinion. But so or so the scenery on all of those routes is quite boring (except near German - Czech border through the Elbe valley).
I would also suggest Dresden. IMO more interesting for tourists than Leipzig.
If you wanna use a nighttrain then from Prague you could go to München and then take the nighttrain from there to the Netherlands.
Tickets bought fixed advance would likely have cost much less as this 1-MO pass.
Brno (in fact stayed there a few weeks ago and have been there many times) is not overly attractive. IF you want a smaller CZ town, try Olomouc. But you can in 1 month easily add more countries: fro Krakow-bite the bullet, pay a little for bus: Zakopane-border with Slovak-end in Poprad (Tatra mountains, big for skiing) Maybe even a short detour via Budapest/HU-Wien/AT-on to CZ.
IF you want to experience what that is-this overhyped nightttrip in a sleeper: best would be from Slovakia to Prahy, arr early morning-can still take train back to other towns in CZ. Check how to RES that-for a real sleeperbed better in advance.
Agree that DD=Dresden is far more interesting as L-eipzig.
Note that In PL-PKP ALL longer dist trains must be RES-easy to by yourself at counter-cost is 1 PLN (22 cts) or sometimes free. MOre for INTERnat though. Do not sweat it-there really is no need to arrange that all weeks ahead-I did it whilst in PL when the train was already moving coming from further onward.
Come back from DD: go in datyime via (once KarlMarx stadt=now Chemnitz)-Nürnberg- to M-ünchen, Make an odd short stop in what it fancies you. Overnite ICE @ 0.01 (seats only, no need for RES) to K or D-üsseldorf, then onward to NL. Do some shopping in DE as prices are lower there for many things as in NL.
Along the Rhein is mid-winter nothing to do and most things closed.
I would stop in Dresden instead of Leipzig :)
From Dresden you can catch a Intercity to Hannover (Change here)for a Intercity via Bad Bentheim, Ammersfort to Amsterdam and finally connect from Ammersfort or Amsterdam to Rotterdamm.
If you wanna Include a Nighttrain experience you could go from Berlin first to Krakow (one direct train per day) and visit then Warsaw and catch from here the Nighttrain to Prague (or Vienna) :)
Other Nighttrain you may use Vienna - Linz (connection from Prague) - Regensburg (connection from Prague) - Amsterdam
For example then NL - (Osnabrück) - Hamburg - Berlin - Krakow - Warsaw - Prague - Brno - (Vienna) - Nighttrain to Amsterdam
Another option is to “just pass” Berlin on your Eastbound Journey Hamburg - (Berlin) - Warsaw or Krakow and go then from Prague to Berlin and finally from Berlin with the direct Intercity back to netherlands
