@Lucie I’ve never won the grand prize before, but was lucky to be the top 10 finalists 2 years straight (2015 & 2016, the waffle pic) But i could give you some tips u to try out for next year :D
1) Plan out your meal and stick to a theme (besides the main theme). If my meals are american, have an entree, side, veggie and in this year’s case, a dessert. Small portions, but filling enough for 1 sitting.
2) Even if the food may be unjapanese, place some japanese food styling elements here and there. Like roll it neatly, learn to carve veggies not just use a cookie cutter, use seeds and natural elements like edible flowers and leaves. Japanese love to observe the seasons in their food, clothes etc:D
3) Arrange your meal neatly and let you eye be your guide. Do you want to start from down to up? Left to right? Diagonally? Mine i use a circular clockwise since my bento is square. So my focus starts at top and circulates around.
4) Now with all your hard work from cooking, carving, thinking and arranging. Don’t hesitate to support and allevate your food at the base. If your food is sitting too low and hiding at the corners, nobody could see your hardwork! It is a food photography contest after all, shadows are not our best friend in a bento picture.
5) With that in mind, use good bright natural lighting, dont use flash (it’s too harsh), and keep your background clean and simple, but not boring. I use simple fabrics :D
Hope this helps! and i wish you all good luck next year!