we got a heap from toys r us, ebay is also good but some of the prices are a bit exxy

a little OT but how well do we think they would stick to / look on brick?
both the kids' bedrooms are all brick... i imagine they would still go on ok just not look as 'fluid' or smooth as on a normal wall?
has anyone tried that?
most wont stick to a brick wall, we tried to put some up when DS was born, its usually to rough to stick to it.