Once upon a time, there were Lego sheets made that looked like Lego bricks stacked together. There were also Lego Bionicle sheets made, too. I have seen Lego fabric but it is from Japan so it would be pricey if you can find it. You may find the sheets on eBay.
Otherwise, you could do rectangles with smaller rectangles on top like the studs on the Lego bricks. I am pretty sure this is the same thing everyone else is describing. Good luck!