Sweet Sixteen Dress Help

I will be having my sweet 16 in october and my two biggest obstacles so far are the colors and my dress. I have settled on using blue and silver as my theme...hopefully it will look ok and I WAS WONDERING if any one knows any websites that will allow u to send a picture or pictures or even sketches of a dress you would like and make theme at a lower cost than the origional dress. I would really apreciate it if any one could send me to a good legitimate site.