By default Nautilus stores thumbnails in ~/.cache/thumbnails folder. It has many advantages, but one place it doesn't work well is with network shares full of multimedia accessed by WiFi by several clients.
It would be much better to let the file server generate the thumbnails locally and store it along the original files (just like Windows is doing with its
thumbs.db file), so clients wouldn't have to download much of the folders' contents just to generate the previews.
Is this option available at all? If not Nautillus, then maybe Thunar? Nemo? Whatever?...