If your kids are anything like mine, they come home with so many treasures from school every year that I have no idea where to store them all! So we have a fun rule at our house --- you can keep it if it fits in the memory box. Now I'm sure to make their memory boxes fairly small -- usually I recycle an old candy box or something similar.
Now at first, this seems almost impossible because most of their treasures are huge paintings or projects --- but that's what the computer is for! The memory box is perfect to store a flash drive, CD or photos of those treasured projects. My kids have become pros at taking pictures or videos of their items so that those memories will fit in the box! Of course, we also have lego guys, pencils, rocks and other small items in there too!
Here is a quick example of what our memory boxes look like - you will see that I keep them simple and flat to make storing them easy. No use to make them really fancy with lots of dimension -- because that would just get squished over the years! The School is Cool line is perfect --- in fact, I would make multiple boxes at one time so they all match!