Thimphu's main post office is the unlikely location for one of Bhutan's most unique gifts. Bring a favourite digital photo on a USB stick or have a portrait taken on the spot and staff will print you a sheet of personalised stamps with your photo on them. The process costs Nu 200 (the actual cost of the stamps) and takes just a couple of minutes.
The shop also sells postcards, which you can then post back home using stamps with your likeness on them. There are also a few first-edition stamp sets.