I found what look like an 80's or early 90's prom dress at the Goodwill a few months ago. It is velour and black.
I didn't do much to it but I like the way it turned out. This took me about an hour to revamp this to a Lolita dress.
First I cut off the black rose that was in the middle of the chest and replace it with a metal cross.
Since there was a mini petticoat built in I sewn in two layers of purple cotton fabric under it. I then sewed a some black lace to the bottom layer of fabric and some black and purple lace to the top layer of purple fabric.
It still didnt look the way I wanted so I cut the velour dress front to have a peek of the purple. I then took the black rose and sewed some purple lace around it and sewed it the smallest point of the slit.