I'd first check with your local government - the entity that issues building occupancy permits. Depending on how the area is zoned, they may have restrictions on the type and size of sign you can post. My shop was in a joint residential-commercial zone, so they were somewhat particular about my sign. It had to be approved before I made and mounted it.
I didn't want neon or an illuminated sign, as it didn't fit with the style I was trying to create for my shop. So I had a local sign maker turn my logo into a large dimensional sign (not completely flat) that mounted flush to the building side. My shop was also a custom-order shop (by appointment only), so I was not as concerned about the sign needing to generate walk-in traffic, as I didn't serve the latter.