People often ask me what I use to prop up knives to show them at an angle. A company called DAP makes a reusable putty called BLUESTIK that works perfectly for this purpose. See: http://www.dap.com/product_details.aspx?BrandID=65&SubcatID=10

Photos such as the one below make use of a ball of BLUESTIK to prop up the knife at a slight angle: