I myself would prefer a JSK or a short sleeved OP, with a slightly lower neckline (but NOT revealing) and something not too dark or black (Maybe a light sky blue with motifs such as roses) but also not over the top. I think something along the lines of MM or IW or VM or this dress from AP.
I like the idea of floral print fabric, but cuter print fabric and plain coloured fabric work as well.
Headdress, I was thinking of a pillbox hat with some of that netting stuff attached, or even mini-top hats with feathers! Go Fascinators! ^^
Any other thoughts?