Neat idea - they look like grownup legos!

That said.. meh. They're not attractive and for the effort, I'd rather go with a commercial SRW block. How much concrete are you generally dealing with that you're looking to get rid of? Several of the concrete plants around here empty the trucks into bigger (at least 3'x2'x2' if not bigger, it's been a while) molds with a semi-cheesy stone texture stamp on the side. While also not gorgeous, they have the advantage of sheer mass and can make one heck of a solid retaining wall. Techo-Bloc's "Monumental" is similar, and what I like about it is it doesn't require geogrid. Of course, those blocks are crazy heavy.

Thanks for your input, I have been looking for a mold that creates a block that weighs under a 100 lbs, but not to small or I will need to many of them. Even the tailings from the pump truck weighs over 300 pounds they leave me on site every time they cleanout.