Here are a few ideas;
1st: you can use the cieling tiles (the ones that look like cottage cheese)from the hardware store mounted on firing strips or glued to wall; the great thing about this is that they are flame resistance so if you want to steam your blocks while hanging no problem there.
2nd: you can get the really long window roller shades and put flannel on them
3rd. You can mount a piece of wood and mount clips on it and attach fabric to that along your cieling