You'd reach a wider customer base if you set up an Etsy shop, then had your images printed to order at Vistaprint or Staples. You could also have your photos printed on apparel or other items at CafePress.
Too valuable to display on USMB.... uh.
You can simply downsample the image or watermark them.
It's not rocket science. You can see low quality, or watermarked fine-art photos all over the net. They are literally everywhere, and that is how they are displayed to sell. You can't sell anything without someone being able to view it.