I think the manufacturer recommends that these be placed on shelves to get the best out of them. However, my friend has his on brackets and they sound fine. The brackets he got were from Argos and were only something like £20 for the pair.
i am using (temporarily) a pair of these tv brackets (follow the link below) which are extremely sturdy as they can be fixed to the wall with up to 8 screws - a few blobs of blutack and you're done - i sprayed them with a few coats of Halfords car paint and clear lacquer to match the front baffles of my speakers and they look great