I had them use heavy weight paper for the base and gave students scrap paper from the scrap paper box to make their sculptures.
2nd grade created some fantastic mixed media Mixed-Up Animals!
Decorative marbled paper:
Mix shaving cream and your choice of acrylic or tempera paints. I used a tin-foil pan to mix it all in. I left the mixture in a the tin foil pan. Then students dipped their paper into the mixture, scraped off the excess paint and shaving cream to reveal their beautiful decorative paper.