STYLETHREAD -- LET'S TALK SHOP!

I ditto heatherlynn on adding a ribbon.

How about a vintage brooch either at the base of a spegetti strap, or at the center of the empire waist?

I think using ribbon and brooches are great ideas.  Maybe you can try using a wider ribbon to cover the straps as well.  Or getting some silk flowers or other detail to add along the hem (that's what I did in high school to get my dress through 2 proms a few weeks apart).

This dress has little rhinestone clasps at the bottom of each strap and then a thin belt of rhinestones under the bust. 


Maybe something like this would work if you were able to get a complementary fabric for the draped scarf:


Or you can try using a scarf, wide ribbon or scarf-and-pin combination to create a dramatic belt or bow:


Or contrasting colors at the waist and hem:


This could be difficult but you could try getting some strands of rhinestones or other beads and attaching them to the straps and then across the back like this dress that Jennifer Lopez wore to the Oscars:

I really like the ribbon around the waist idea. Do you want to stick with a long dress? Iron on hems could work if you won't want to sew and want to keep it a long dress.