I've just put up 3 boxes for sparrows on the north facing gable end, they (sparrows, not gable ends) are sociable and like to nest in groups. I was going to make some, but went to garden centre for plants and saw they had them for less than the wood might have cost me. Seem OK.
Now I'm worried, the ones I put up are are purely functional and a bit boring so if anyone locally has bought the posh ones the sparrows won't want to use mine.
Seriously though, I think of bird boxes as something to help the birds, not a fashion statement by the property owner. If I had £100 to spend, 10 boxes to suit a range if species would be more use than 1 fancy one.