I have a friend who is wanting me to make a cake for her 2 year old son who loves Thomas, elmo, cars and trucks but she wants me to put as many things as possible on the cake any ideas how i could pull this off for her?

I've always thought the spiral cakes were so neat.  Since see wants all wheeled vehicles, maybe you could have them coming down the spiral path. 

Take advantage of your cake board.  I've seen many decorators using this space to carry out a theme - for example, a train track around the board with Thomas and his friends rolling around it  (no load to the cake), with the cake acting as a mountain or other backdrop.  Good luck!

Don't know if you've done this already but...how about a toybox? and toys scattered on cakeboard.