phunky,
Hey babe! Before you determine a costume here are things to concider....
Is the opening a themed event? If so, you must stay in that theme.
Leather can be limiting. It can be tight, it can be kind of bland in colour options and it can be pricey. Do not limit your mind to that where there are so many cool fabrics out there as well.
What type of audience determines what style of costume as well. For instance, Glow worms catsuit wouldn't be suitable for upscale or child friendly place.
Normally when someone says "dress up" they mean to dress nice, otherwise they say they would like a costume. Do not be afraid to ask for more specifics, so that you can better serve your coustomer.
Other things...shiny is good with fire, but not overdone. Same thing with dark colours.
Remember to accessorize but not overdo. Body paints don't work in every environment, neither does any form of nakedness (No shirt, no shoes policy can still apply to performers where the health boards are concerned).
My suggestions are to get more info from the person who hired you on exactly what he is looking for. Then you will be in a better position to create the ideal costume.
Need to go finish beading mine now! 
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Pele
Higher, higher burning fire...making music like a choir...
http://www.pyromorph.com