I was going to suggest PVA as well - we add this to our paint quite often, especially if we want a shiny finish.
Good suggestion Nic, I have just finished drawing some of the animals for Rumble in the Jungle. We are turning the home corner into a jungle and the children will be painting the animals in the story to put around the walls. They will also be making vines and flowers. We are using a green net on the ceiling with vines, snakes etc., hanging down. The children will bring in their own cuddly animals from home to play with in the jungle.
By each of the animals I will be printing the verse from the book. The last page is to be a large card for when the area is closed each evening.:frog: