Had my sister's baby shower in October. Since we didn't know the baby's gender, we did an ABC Block themed shower. The invitation had green and brown A-B-C Blocks on it... the attached photo is the centerpiece I made for the gift table. The blocks match the blocks on the invite. It's made from 2 green styrofoam cubes (purchased at Michaels). The front of each block is covered with brown paper (purchased at Michaels) and then I painted the dots (on top block) and stripes (on bottom block) on the sides of each cube to match the invitation. The letters are styrofoam letters (also purchased at Michaels) Then I stuck in the parasol and hung plastic rattles (pacifiers would have been cute too) from the spokes.
The centerpieces were inexpensive teddy bears I found online. Each teddy bear had an ABC block (favor plastic cube purchased at party store) around its neck. Then we attached a pink and blue balloon to each bear.
I specifically wanted to share the gift table centerpiece because you can really apply the idea to any theme. People loved it--and my sister now has it in the baby's room. (conveniently the baby's room was painted a light green!)