Gabriel's ninth birthday was a 'block party' (legos, not the whole neighborhood) and the cake was GREAT! I used a white cake with strawberry filling between the layers. The buttercream icing is colored using gel food coloring, and the colors came out PERFECT! The supports in the middle were a challenge of their own, since the cake layers didn't bake up to the usual height for the PVC supports I had planned to use (humidity probably played a role in this). I spent some time trying to think creatively, to come up with something else that would act as supports inside the cake - had to be something dishwasher safe and with adjustable height, but not too big around (didn't want to damage the cake any more than necessary).....
Finally, the lightbulb clicked ON inside my head: LEGOS! Seems obvious now, right? Legos inside of a lego cake - DUH!
The circles on top of the blocks were made with a 'molten-n-more' pan, to get good cylinders (cupcakes would have worked, but these looked so much better!) It was tough to get them frosted, but the result was still yummy. :)