This is what I do....
Chose a theme and or color scheme. I find that bright colors go over best. And for every show I use a black velvet cloth that I lay over the white ones that are provided. This really makes your flowers stand out AND your booth, even from across the room.
I have a show tomorrow and our theme is Oriental. Our colors are red, blue, and green.
At the end of the month we are doing a butterfly theme with yellow, purple and green our butterflies will all be monarch to add a pop of orange and to keep the butterflies consistent which will make them stand out more.
In the past we have done....
vintage with whites, ivories, light blues, and peach used lots and lots of pearls, feathers, and metallics.
citrus theme using yellows, lime green, hot pink we used real fruit and faux fruit in our designs
We are known for our bing and wire work so we did a show themed around that. We used all turquoise blue wire and our flowers were orange with a pop of lime green. We used lots of bling, wire, and crystals. Each piece we did had one, two, or all three of the elements.
When we first started doing shows we only chose a color and not a theme, we did an all red show (lots of different shades of reds and we popped with lime green)
We did an all white show (which was the least well received show we have done to date.)
Oh and besides the theme and colors we rarely have a design plan. We "wing" it. We find our best work comes from when we line the buckets of flowers up and let our design instincts take over.
We always order flowers in that are a mix of "normal" flowers we have on a regular basis and "cool" flowers we rarely have or have never had at all.
We make a point to be sure our designs are not of those we have done before, especially for a wedding. We do what the brides call "funky" designs, and they LOVE them. We figure anyone can picture in their heads what a "ball of flowers" bouquet looks like, so we do stuff that is different things people in this area are less likely to see. Not to say we don't do "ball of flowers" designs, but they are always with a twist. And we are careful not to go too crazy that the brides in this area will think we are the designers who do strange work, we just take our normal weddings work and turn it up a notch.
Hope this helps. My best advise would be to get a black cloth (velvet if you can) to put over the white table. It will really make things pop.