I saw a system at the Utah Expo called Skull Max that looked to be the most versatile in that you can adjust it any angle or direction. I believe it was a bit more expensive than the Skull Hooker as they had those at another booth. I liked the Skull Max in that it utilizes a ball and socket type setup so you have unlimited adjustments. I just looked at their website and quite frankly it is horrible as you really cannot even see what it looks like so not sure if it helps at all to visualize it. Anyway if I had to mount one and wanted to be able to perhaps change the angle periodically or be in a unique position (and if money is not an issue) I thought they looked to be a great system. Obviously no personal experience.
Funny I was just going through some things this evening and found a speaker wall mounting kit I bought several years ago for mounting bookshelf speakers on the wall. It looks something that could be adapted to mounting a euro on the wall and looking on ebay, they appear to be less expensive. Would have to do some custom work to attach the skull to it but that's just another option. I think they usually are rated by how much weight they can hold so you'd need to find one heavy duty enough for the piece in question.