..and while I'm still on the subject of Nordiska Museet:
They have a database with items from the textiles collection where you can find a few goodies but the search engine and interface is not exactly user friendly.
I'm not able to link to the results so I'll hold your hand while you explore the collections on your own.
Go to the search page of Textilgalleriet and switch to English in the top left if you prefer it that way.
I haven't explored the collection very extensively but you'll get some nice search results if you just enter "18th".
The search result will bring you 17th, 18th and some 19th century items. Don't expect actual costumes, but some highlights are many fine examples of embroidery (don't miss the adorable lion!), block printed 18thc fabric, lace and a fragment of a jacket in matelassé technique.
Big Plus: The "magnifying glass" feature lets you examine the objects very closely
Many objects have additional images
Big Minus: The programming is very confusing! Whatever you do - don't press the "back-button" in your browser when you wish to get back to the search results! It will only take you to the front page and you lose all your results.
Instead, when you're done viewing an object, you click "New Search" in the bar above the object. I know - it doesn't make sense, but it takes you back to the search results nevertheless.
There's also information about different textile techniques in the "Techniques" tab, unfortunately in Swedish only, except for an article on Swedish embroidery.
Overall - definitely a step in the right direction! And maybe, one day, Nordiska Museet put all of their costume collection online.