Does the faa restrict any non-aviation items kept in a private hangar?

eferrell has it correct, the FAA could care less what you keep in a private hangar. In most cases the hangar owner or the airport will set restrictions. Some insurance even sets restrictions on what can be stored in your hangar. Some "local codes" from your city or state may also restrict what can be kept in your hangar, fire codes often restrict the amount of fuel (not in the aircraft) that you can store.