Introduce a Disposable Camera
Your child has a unique point of view. Let them capture it with a disposable camera and an afternoon wandering around your house and yard. (Or, take them to a beautiful outdoor space like a local or national park). Try not to give them any instruction on what to capture and see what they come back with. If they need a little direction, ask them to take a few pictures of things up close and things from far away.
You can also encourage your child to bring a camera with them everywhere they go for a week. At the end of the week, print out the pictures and ask them to make a collage using cut-outs of the pictures and art materials.
Use the Sky
Have you ever laid on the grass and looked up at the sky for hours or even minutes at a time? Take your child outside on a cloudy day and try to find clouds that look like familiar things or shapes. Maybe they'll see a pirate or a flying duck and an ice cream cone. Use the things your child sees to make up funny stories about pirate and ducks and ice cream. In a similar vein, go star-gazing in the wilderness and use the stars to make shapes by connecting the "dots" (aka stars). Make up stories with the dot shapes, instead.
Create a Dress-Up Corner
Instead of throwing away old costumes or clothes, keep them in a dress-up corner for your sons and daughters. Old sports items like goggles, ski masks, flippers, and tutus can add to the fun, too. Leave it out and you'll be surprised at how often your children gravitate towards the box without any prodding from you.
Make Instruments and Put on a Concert
If you have old containers (like cereal boxes, oatmeal or ice cream tubs, and Pringles cans) you can use scissors, tape and string to make your own instruments. Don't provide instruction and see how your child makes a functional drum, shaker, or flute or guitar. Make a variety of instruments and put on a concert. Take it a step further and make up a name and back-story for your family band!
Use Boxes to Create a Made-Up World
If you've ever given a large gift for a holiday and seen your child become more interested in the huge box than the gift, you know that boxes are great blank slates for creativity. Gather different sizes and shapes of boxes and take a day to create a made-up world in your play room or backyard. Provide scissors, tape and markers to alter the boxes. You may find you and your child creating streets, neighborhoods, castles or enchanted forests.