I loved using shrink art plastic when I was a kid and thought it would be fun to use the stamps and create some shrink art hair accessories for my daughter. She was amazed at watching the transformation as the plastic curls up and then shrinks down flat again (that always amazes me too!). Here's the steps that I used to created the headband and barrette set.
SUPPLIES:
Shrink Film Plastic (not shown), which is available at most craft supply stores.
Stretch Thread (this is used on the headband and while regular thread may work, I thought this might work better and not cause the plastic to "pull" on the headband.
A strong glue (Crafters's Pick is my favorite).
Small Hole Punch (1/8" size)
Detail Scissors.
Sewing Needle.
Stretch headbands and a set of Barrettes that have a flat surface for gluing.
You will also need (not shown):
Stamps. I used Ribbit for the headband and Flower Garden on the barrettes.
StazOn Black Ink
Fine Sand Paper. 400 or higher
Colored Pencils or Permanent Markers
This is an important step: Rough up your Shrink Art Plastic with the fine sandpaper before stamping or coloring. I purchased an InkJet Shrink Film with a matte finish (like this here), but the surface was still too slick for use with the colored pencils, so I did the sanding procedure. Regular shrink plastic will definitely require this step.
Stamp your images on the Shrink Art Plastic using the StazOn Black ink and then color in your images. I had my daughter do some of the coloring with me. We used colored pencils, but I understand that permanent markers work great too. Regular markers will probably not work on the plastic.
Cut out your images with the fine scissors, leaving space for any holes that you may need to punch so you can attach the images to the headband. (see the side of each mushroom where I left a tab for the hole punch). Punch your holes BEFORE you shrink your plastic.
Shrink the plastic following the instructions on the Shrink Art Plastic. Allow to cool completely.
Gather you sewing supplies for the headband. I added a few applique flowers to the headband as well.
Attach the shrink art, applique flowers and any beads or other embellishments to the headband using the stretch thread. I added beads to the top of the holes on each side of the mushrooms. Remember that the headband will strech when it is worn, so keep that in mind when you are spacing your items.
Here's the finished headband. You can see how the spacing of the shrink art really expands once the headband is on.
For the BARRETTES: Follow the same process for stamping, coloring, cutting and shrinking your artwork. You do not need to use the hole punch for these as we will glue them in place.
Here's a close-up of one of the finished flowers. Have fun with the colors!
Apply a liberal amount of the sticky glue to the top of the barrette. Crafter's Pick is great as it dries clear, but holds almost instantly, so the flowers won't slip off as it dries.
Start in the middle of the barrette and work your way to the outside of each edge.
SPECIAL NOTE: When gluing the flowers, be sure to think about how the barrette will be put in your hair and orient your flowers based on the direction it will sit in your hair. One barrette will open to the left and one will open to the right.
Here's the finished barrettes on my beautiful daughter. These would make great take home gifts for Birthday Party guests, or even a fun project for older girls to do at a birthday party and create their own hair barrettes.
This is an important step: Rough up your Shrink Art Plastic with the fine sandpaper before stamping or coloring. I purchased an InkJet Shrink Film with a matte finish (
Stamp your images on the Shrink Art Plastic using the StazOn Black ink and then color in your images. I had my daughter do some of the coloring with me. We used colored pencils, but I understand that permanent markers work great too. Regular markers will probably not work on the plastic.
Cut out your images with the fine scissors, leaving space for any holes that you may need to punch so you can attach the images to the headband. (see the side of each mushroom where I left a tab for the hole punch). Punch your holes BEFORE you shrink your plastic. 
Shrink the plastic following the instructions on the Shrink Art Plastic. Allow to cool completely.
Attach the shrink art, applique flowers and any beads or other embellishments to the headband using the stretch thread. I added beads to the top of the holes on each side of the mushrooms. Remember that the headband will strech when it is worn, so keep that in mind when you are spacing your items.
Here's the finished headband. You can see how the spacing of the shrink art really expands once the headband is on.
For the BARRETTES: Follow the same process for stamping, coloring, cutting and shrinking your artwork. You do not need to use the hole punch for these as we will glue them in place. 
Apply a liberal amount of the sticky glue to the top of the barrette. Crafter's Pick is great as it dries clear, but holds almost instantly, so the flowers won't slip off as it dries.
Start in the middle of the barrette and work your way to the outside of each edge.
