Agree with the others, under a year, they'll be happy with just the egg. For older kids, I'd say 4+, you could put little erasers that are shaped like bunnies, or eggs. I know my kids get stuff like that all the time in goody bags.
If you really want to put something in the eggs for the little ones, how about those Gerber Graduate puff things that melt in their mouths? Or Cheerios.
Start (2/1/13): 280
| Pounds lost: 11.3