For my son's third birthday I decked the house with dinos. The kids and grown up loved the theme.
My son, he LOVES dinosaurs. The color scheme was built around the invitation.
I made everything except the invitations and the party favors. You can see all of the DYI details and links to sources on my blog, www.namesakedesign.blogspot.com.
The dinosaur painting - the kids really got a kick out of this.