Balloon decorations are a cute shower addition and especially fitting when kids attend. Have your local balloon store create these, or try your hand at balloon twisting. It's easier than you'd think.
The key to balloon twisting is to leave your balloon a bit underinflated. A bit of experimentation and you'll hone in on a proper look. YouTube is a great resource for balloon twisting videos!
Balloon twisting creations
Here's a few quick examples for adding twisted balloons to a shower: