Dang I didn't know my sexter was so hot!
I don't think black tights would look right...
I also think a cardi would be weird because the dress is no where near casual
What about those wrap things that go around your arms or your shoulders if need be
Something like this but a little wider sorry I'm not sure what they are called and I can't pip from my phone
http://www.google.com/search?hl=en&client=safari&gl=us&biw=320&bih=416&tbm=isch&sa=1&q=dress+shawl&oq=dress+shawl&gs_l=mobile-gws-serp.1.0.0j0i5l2j0i24l2.14145.16600.0.17774.10.10.0.0.0.0.466.1561.0j4j1j1j1.7.0...0.0...1ac.1.LxOdI6fgYt4#i=0