Wonderful job on the planter. You obviously have a talent for doing them.
As far as the flower show goes have you been to it before? It is a little difficult giving advice as everyone does things differently.
The only pointers I can give you is keep it simple. Choose cloths/backgrounds that set off your displays and try and keep them relevant to any theme you may have. For instance if it is a Christmas theme then use red, green, gold, silver or you could go for a 'natural' look using a backdrop of seagrass and then decorate your stand with lichen covered twigs, mistletoe, rosehips etc.
Keep your display uncluttered so people can see each exhibit properly.
Use different heights to display things. Lets say you have three planters, one small, one medium, one large. Display them like a waterfall (does that make sense
) Make sure you have all relevant information to hand for any interested customers. Prices, time etc.
The most important one of all...make sure your plants are in tiptop condition. Give yourself time for a last minute check on anything you are displaying to nip off a shrivelled leaf etc.
I hope some of that is of use to you....One last thing....enjoy yourself! If it doesn't go to plan think of it as a learning curve not a failing!