Cinnamon - imo, black opaques are too harsh against the fabric. I wear either:
Brown opaques and brown ballet flats or high heel Mary-Janes.
I have just bought a pair of bright opaques - the same shade as the flowers - to wear with the dress. Will either wear with black or brown heels - whichever looks best and possibly mid-calf biker boots - to give it more of a funky edge.
Would also look great with a pair of close fitting brown knee high boots (as opposed to the slouchier styles around).
Layer it over a long sleeved tee - a warm cream, brown, bright purple or even green.
Cardigans - bright magenta round neck (with satin covered buttons to work the whole 40's thing - got mine in M&S). Looks good with a skinny belt around the waistline of the cardi too. Have an oversized chocolate coloured waterfall/wrap cardi which I have worn loosely over the top and also cinched in with a large brown belt.
In term of accessories - keep it simple - the dress is the focus. Generally I leave them out but I have worn both a long string of pearls knotted at the chest and a pearl 3 strand bracelet. Not together though - that would be too much like "dressing up like granny" You want a nod to the era rather than am-dram queen