Here is a set of 26 box templates, one for each letter of the alphabet, available from my Etsy store.
They make a nice wrapping for a personalized gift. You can use them for initials, spell a whole name or even a little message:
Here is a video for a closer look:
They are about 5cm (2″) high when printed in A4 / US letter format. You can print them larger, of course, but you will need a printer which can handle the larger sheet size. If you don’t have access to one, most local print shops can easily print larger formats.
For the original size, I recommend 150-180gsm cardstock (about 65 lb). If you scale them up, use stronger cardstock, otherwise the boxes will be prone to warping.
You can fill them with all kinds of things, for instance little toy blocks:
Here are some more examples of some boxes:
You can get the set of all 26 templates from my Etsy store. If you are on a budget, you can buy individual letters there, too.