I'm actually on an interrail holiday right now! You can buy a five days in ten pass, but book Eurostar separately as the Interrail supplement is more expensive than most tickets.
I'd suggest Vienna, Salzburg, Nuremberg if you want it, and work your way across Austria and Switzerland to Belgium if you have a pass. Don't go through France if you have a pass - you have to reserve on TGVs and it's very expensive on top of the pass.
If you want stunning scenery on a trip, do go to Italy. DH and I were very glad we had a compartment to ourselves between Munich and Verona, because the noises we were making at the scenery were not dignified. (We kind of lost the power of speech and were "oooh" and flapping hands at each other.)
But my number 1 piece of advice is go to www.seat61.com
. The man who runs it is a train travel fiend and we have taken so many holidays using his website.
(Current holiday is London-Germany via Brussels, Germany-Northern Italy, and we're off to Switzerland on Friday to see friends, before home via Germany and Belgium.) previousky we've done London-Zurich via Paris, Zurich-Salzburg, Salzburg-Vienna, Vienna-Munich, sleeper to Paris, home via Eurostar again.
Also, if you can afford it and are doing long journeys, splurge for a first-class pass. It's less than €150 euros more and is worth every penny in terms of comfort and ability to get a seat.
If you're only doing a couple of long journeys, don't bother with a pass. Book your tickets in advance, it'll be much cheaper. If you decide to go to Bruges and are heading directly from there to London book "any Belgian station" to London. Only £5 more. Also, bahn.com is a wonderful resource for planning as it has all the timetables for Europe. The app is very useful if you have a smartphone.