Oh, you're going to have a good time!!! I have veggie cupcakes and a cake in my photos and they remain some of my favorites!!!
I just took a big chunk of gumpaste and colored it red, green, yellow, orange, purple and then played with it. Then once they were dry, I placed them on the cake or cupcakes and used buttercream (green) for the leaves. Could I have done more or fancier? Yep, but garden cakes are cute and fun!!!
Green onions - roll out a very thin snake of gumpaste and fold in half. Let dry flat. The folded section will get inserted into the icing.
Tomato - ball of red!
Peppers - oval of your color of choice, use a toothpick to score lines.
Cucumber/squash/gourds - roll a log, thin at an end for a squash or curve a bit for a cuke
Eggplant - oval with one end larger than the other
Pumpkin - orange ball, score with a toothpick
Brocooli - dark green balls smooshed together, dot with a toothpick for texture, wrap with green leaves
Cauliflower - white ball, dot with a toothpick, wrap with green leaves
Cabbage - leaves formed around a ball, starting from the inside working out
Have fun!!! I can't wait to see a picture!!!