A $13.00 bass, 3 Seagull guitars, a tenor guitar by Harmony, a bodhran, and a $0.50 mandolin...I'm lucky enough to have an extra closet to store my "arsenol" in... in the cases, leaned up against the back of the closet, case-handles out for easy grabbin...
I do plan on getting a hygrometer so I can keep that correct too, but that's not such a going concern here except in winter...
I'd NEVER store an instrument I cared about on a hook on the wall... 1) I don't trust 'em to not fall out (but that's just a paranoia thing) and 2) dust, humidity, accidents, unwelcome fingers are all too hard to prevent when they're out in the open...
I feel better if they're kept out of harms way...