They're plastic perler bead Christmas trees hot glued to Wild Wasabi & Real Red cardstock. if you have kids 10 and under, chances are you have a bin full of these in your craft bin. Kids, especially boys, are very into pixellated graphics thanks to the Minecraft phenomenon. So these graphic looking designs are much appreciated among their circuit.
You could easily swap out the plastic beads for buttons or small circle punches (like a hole punch size) to make these also. I think it's important to keep the kids interested in our craft, so even the most simplistic card is a little work of art that puts a smile on everyone's face.