It depends, analog gonverted batcoins produced via a computer output perephiral are indeed stackable. Digital ones are stackable via the use of digital image manipulation software or div code z axis layer positioning. The number of stackable coins varies on format, the digital ones mainly being dependant on how many your computer can render at a time. The stackability of the analog ones depends on the medium used to reproduce them. For example, if they are reproduced on standard printer paper, you should be able to stack about 90,000 of them before the stack starts to be adversly affected. At such time of course the value of the ink you expended is probably more than the value of all batcoins in existance, ever, but you totally could do that!
I suppose you could print otu a bunch of batcoins and make a collage picture out of them and sell it as art and accidentally increase their value.