There are some very interesting ideas here. I need to get something going as of right now the old blades have been put back in their wrappings and are on a shelf in the bathroom cabinet away from the sticky fingers of my childrens.
I assume there's no blade slot in the new house's medicine cabinet. So I Testor's model glued the lid onto a green Kroger vitamin bottle (de-labeled) and Dremeled a slot in the top. Since the blades have room to stack flat inside, I reckon it should be good for, oh, at least two years.
For an ironic style look, you can use a Spam can. Best part is, you can just cut a slot in the top and don't have to empty the can since - internet fact! - the synthetic meat-like contents cannot decay. Just stuff blades down into the Spam. It stops the annoying rattle of loose blades and, as a bonus, helps cover the smell of Lilac Vegetal.
Just make an origami water bomb and cut a slot in it for the blades. There are instructions all over the internet on how to make the water bombs. Scale up or down as needed by using different size sheets of paper.
Well.....The space between studs is about 2 feet and the height of the hole is about 5 feet high. That I believe gives me a space(If my math is correct) of about 1440 square inches. I pretty sure you can fit 400 bare DE blades in a square inch but let us say 100 will fit. I shave everyday and change my blade every two or three shaves. So....I think by the time it fills up, I would be a head in a jar by then and make my robot deal with it.
I use Altoids tins. When they're full, I seal them with duck tape, mark them "Caution - Used Razor Blades" with a big, heavy Sharpie (I alway thought that was ironic), and put them in the recycling bin.
I drop mine in an empty beer can, my neighbor works at a hospital and will take it to throw in a sharps container.