You could probably get away with 1 nozzle every foot or so. It's pretty easy to add another nozzle to an existing bulkhead if you ever needed any more. Don't forget that the misting system needs its own separate reservoir with RO/distilled water. Looks like you have plenty of room under your tank for a 5 gallon bucket though
I am ready to order some more misting nozzles,but before I do I need to know if the mist from the nozzle will reach the background that is 19'' from the nozzle.If not I need to get 4 quads and 2 doubles.
I would think that they would towards the bottom but I'm not so sure about the tops of your walls as the droplets/spray pattern would be falling over distance. If you are using good internal circulation fans they may alleviate that somewhat.