I'm still informal enough that I don't want my linen napkins to be perfectly starched and ironed. I like it when they're freshly washed and (hopefully!) hung out to dry in the sunshine. Just fold them into a rough rectangle and tuck them next to a simple white plate. So elegant, yet relaxed.
Linen napkins can be expensive and can run as high as $50 each if they are made made with high quality linen. Etsy is a good source for less expensive ones but you can also make your own quite easily. If you're sewing skills aren't up to hemming, try just sewing a line all the way around the square, about 1/4" from the edge. The edges will fray after a few washes, but that's also a nice touch.
(Image: Adler & Co.)