In your travels.....start looking in newer housing developments for "bump-outs" hanging off the side of houses.These are used for locating gas,"vent free"....FP's(fireplace).This is just for an idea on looks and design scale.
And if you really want to check one out.....find a place under construction and just ask for a little FP,"look see".
These represent a very nice way to add not only space for a compressor.....but alot of woodwackin dicks use them for dust collectors.Theres a direct correlation between your overall design,your building skills and how "goober" it turns out.The better it looks from the outside(and theres some nice'uns posted above),the less neighbors and or compressor police will pay any attention to it.
There are make-up air issues....IOWs,its 90%+ humidity outside.....are you sure you want to be pulling that through your system?Also think about the convenience of draining tank.....Theres ways around most of these issues,just have to figure whats gonna work best for you.BW