Conclusion

Amsterdam is a great vintage/design-wise city to visit, with at least one very nice flea market (IJ-Hallen). And if you are planning to visit this part of Europe,  a trip to Amsterdam  perfectly fits within a larger tour including London, Paris, and Brussels. All these four capital cities are pretty close to one another, have great flea markets and antiques stores, and can easily be connected within an hour and a half (1h30) ride in train: London-Paris (Eurostar), Paris-Brussels (Thalys), Brussel-Amsterdam (SNCB).