Flip flips / sandals - easy to get in & out of
Sweat suit - if they do the weigh-in in your posing suit, you'll want something easy to slip over it. Most competitors like to stay covered up prior to the show. Also long sleeves / legs in case you still drying your last protan layer
your posing suit --- make sure its a dark one or have a spare in case you get protan on it
extra protan for touch-ups
Are you protanning your face?
You might want a good dark base makeup as protan can start to crack & streak when you start sweating, or if your face layer isnt' dark enough (MAC women's make up makes great bases -- or if you go to the department store and talk to any of the make up counter people about makeup more for stage / theatrical - they should be able to help you)- people who don't have dark enough tan on their faces stand out under those stage lights - the contrast between face & body becomes vary stark.
other food besides brownies - for ex if there is a big delay in the start of the show or several different weight classes you have to sit thru - make sure you have a complete day's worth of all the food you could possibly need because if you don't have it you may be screwed for time to get it.
at least 1 spare copy of your posing music -- do they require it on CD or tape? Also label it with your name & if you know it, your competitor number to help the (often idiot) people who set up the music for the routines.
small Bag of potato chips - if your electrolytes are too out of balance from your water deplete or your diuretics (esp lasix of something that isn't potassium sparing) - if you start to feel dizzy or light-headed (e.g. this is why you hear about competitors passing out on stage) - you can eat a couple potato chips (not the whole bag) and the salt will help to even out your electrolytes again. - its not a necessity but its a little trick I learned yrs ago from a well-known female competitor / trainer.
A digital camera so we can see your pix!!!!!!!!!!!!!!!!!