Make sure your pageant dress can be age appropriate. Do not put a strapless gown on girls under the age of 12. Spaghetti straps, as thin as they might be, are still a strap. Generally speaking, strapless gowns are most accepted on girls 15 and up. Make sure cleavage is properly covered. Slits and the color black are usually for women over the age of 18. Your judging panel is made up of many different personalities and people.
Choosing a solid colored gown may be a good idea. In a traditional, natural pageant, you want the fabric of your gown to be one color with the beads and stones complementing the style and cut of the dress. The dress should draw attention to you, not draw our attention to the dress. Your gown should make your body look proportional and you need to be able to walk in it comfortably. In natural pageant, do not wear hoops under the ball gowns. A skirt that is too full and big will be distracting to the judges and shorten the height of the girl wearing it.
Make sure the dress can flatter you and highlight your personality. Don’t worry about what the other girls are wearing. I’ve seen contestants blow their chance at the title because they took an unnecessary risk with their dress choice because they thought “different” was what it would take to stand out. Save different for high fashion events and appearances, not for competition.