From my understanding, in San Francisco, CA, there is a code requirement that you cannot obstruct an area within 18 inches of a fire sprinkler. What is meant by obstruction? Say, you installed one of these: http://rakks.com/wall-mounted-standards/
The standard itself is fine, just be wary of what attaches to it
Since a standard that is less than 1" deep off the wall is going to be shallower than a sidewall sprinkler's escutcheon, it will not "prevent the pattern from fully developing", therefore NFPA 13 184.108.40.206 does not apply:
220.127.116.11.1.1 Continuous or noncontinuous obstructions less than or equal to 18 in. (457 mm) below the sprinkler deflector that prevent the pattern from fully developing shall comply with this section.
However, you do need to be careful with how you set up your storage to avoid running afoul of the intent of 18.104.22.168 with the storage itself. I would follow the same 18" rule enforced for standard sidewall sprinklers by 8.7.6:
8.7.6 Clearance to Storage (Standard Sidewall Spray Sprinklers). The clearance between the deflector and the top of storage shall be 18 in. (457 mm) or greater.
It depends on the shape of the spray and the rating of the sprinkler head.
Sprinkler heads are rated for various situations. Based on the head rating, the sprinkler engineer can layout a pattern that “covers” the spaces based on the occupancy rating. That is to say, one kind of head will work in a narrow residential hallway, while another type is rated for business areas with tall shelving.
Very complicated. I’d contact the sprinkler installer. Their name will be on a metal plate chained to the “riser” or where the water enters the building.