With access to a printer, it's easy to make stationery that at least looks more interesting than a blank page. Searching around online for clip art and simple illustrations can produce little items to dress up a page and suggest an atmosphere appealing to the writer. A color printer adds that much more dimensionality to design and flair, but with imagination a black-and-white printer (like mine) is enough to design unusual stationery.
For myself, I found a classical illustration of a Hand of Glory. This was a device used by burglars to silently and invisibly break into homes. One would harvest a hand from a hanged corpse, steep it in paraffin, and use it as a candle in the home one was burglarizing: as long as it burned, the thief was beyond detection, according to superstition. While I don't advocate plundering corpses or breaking into homes, the romance of the times and the sense of mysticism were what appealed to me. Even if one doesn't know what a Hand of Glory is, it's still a supernatural-looking object. I'd place this in the corner of a page and write around it.
Below is an illustration I scanned from The Volume Library (I will always be grateful that book found me), a banner above one of the pages. I cleared out the text within it and filled it in with my own name and address, choosing an appropriate font (probably Copperplate). I simply placed this in the header and printed out one sheet like this--no need to have it on every page of the same letter. Again, it was nicer than nothing. The antique illustration of a candle and a book were up my alley in terms of symbolism as well as aesthetic appeal.