What about dollhouse items or scrapbooking embellishments on the tops of cupcakes or table decor? If you think outside the box, you could do all kinds of great themes.
They are about half the price of designated "this is for a birthday" items I've found, usually come in packs of multiples, and give you a broader spectrum to choose party themes.
For example, if I go with the "children's literature" theme... how perfect would these be on top of frosting?
A "Garden Party":
|$4 on Etsy|
A "Mardi Gras" or Madeline party:
Crayon/primary colors party:
Anything that comes in a "set" for a dollhouse or scrapbook could work!
An "I Love Ikea" party: