I did a baby shower invite once that was a baby bottle (with the shower information on it) tucked into a little baby diaper. Here's the link:
Gallery at Splitcoaststampers
The baby bottle was just a tag I made to look like a bottle. The diaper is a 6" piece of square cardstock cut in half diagonally (made into 2 triangles), then folded to look like a diaper. Very cute and easy - and the only stamp you really need is one that says "for, date, time, place", etc. I'll send you the tag template if you're interested.
Hope your shower goes well!