The spren of Roshar are all some mix between Honor and Cultivation or Odium. The Odium spren look different from the normal spren showing that different shards have different spren.
In Elantris it is never discovered how seons are created. This is likely because they are devotion spren and bond with the people on Sel similar to how high spren bond to people on Roshar. It is also mentioned that Seons are almost physical representations of "Gods love" (Devotion)