Looks cool, but... download link is broken as of this date. FYI.

but how do you EDIT the blocks in the first place

First off, you're missing some blocks. Some of the wool colors (although this might be intentional, trapdoors, regular clay, the other two wood types, boat, minecart, the half stone block, and cobwebs is what I noticed. Move the saplings, they're blocking like 4 of the blocks. You should have one or two crops growing.

If you want some ideas, you might want to make a big wall that has all the painting on it. Also, it'd be kind of cool if you could trap one of every mob in little glass observation rooms so we can see those textures and add in a chest full of all the items that aren't blocks (tools, armor, food, ect) This won't fit in one screenshot, it'll take 3 or 4, but so what?

you should go into your terrain file and arrange as so

Not the best template i have seen...its just the setup, you cant exactly see some stuff with this template