Balloons with photos of memories tied to the bottom is a sentimental and thoughtful proposal idea. Let her pop all of the balloons to find the ring. You can fill the rest of the balloons with sweets, glitter or flowers.
Sheet music instead of a book Storybook Paper Roses bouquet. It would killlll me to rip apart a book for this, but this is SUCH a cool idea cost effective. Smaller ones can be made for the bridesmaids. My only concern is if the ink rubs off on the dress.