Point éphémère in Paris is a great venue. I'm not sure of its capacity but it is 1400 square metres.
L'atelier Tampon gallery is a very, very small but fastastic space on Rue Jules Valles M. Charonne. The couple who run it are lovely, maybe too lovely, and if they haven't closed down the venue is the basement of a small gallery, and i'm sure they would welcome somebody like Geoff Mullen with open arms. White Out played there with Nels Cline in 2006.
Who was that guy who posted on here a couple of times about a mini festival in paris with people like Sunburned and Keith Fullerton Whitman? I'm sure if you got into contact with that guy he would help you out with Paris venues....
EDIT - it was called the Ali-Fib fest. Here is the man's myspace
www.myspace.com/alifibgigs.
i'm not really sure about any other cities, but people will be along soon to help you out no doubt.