Digital BW, The Print

Are you going to be selling the prints, and do they need to 
be "archival"? If the answers are maybe and no, there are several fine 
weave banner materials that would hold higher detail than most canvas, 
and still allow you to stretch them on some kind of frame, or hang them 
like a tapestry. Some of those materials would allow a backlight to 
illuminate them, which might be an interesting effect. There is also 
back light film materials, or if the images fit, you could print on 
silk (but a lot of things won't look right on silk).

And if you want big, and are going to be sending them out for printing, 
why not print them 1 meter (or more) wide?

Since you were quoting metric sizes, I'll guess that you are not in 
America, so getting the same materials that I describe might not be 
possible unless you find a company in the US that will ship to you.