I would get some flowers matching the flower crown, and make a flower-belt type thing for under the top flowy part. Then also add smaller flowers to the straps, if you can. If you can't, then get some stretchy white (or whatever colour the dress is) fabric, braid it, and attach them to the straps. (I'm guessing you're going for the modern "Boho" look )
statement jewelry and elaborate hair!
hm try addign some bold accesories and add a realyl stunnign updo and try over the top makeup and accesories
i wouldnt try to detract from its simplicity its beautiful and you will look so serene in it