RoscoeV - my tank is 3 gal and came with the compressor for my train horns. You can easily use an inexpensive portable tank like Harbor Freight sells and with a few quick disconnects still use it as a stand alone portable tank.
336 - I understand your compressor is continuous duty, that just means it can run 1 hr without a "rest" before resting for 1 hr according to Viar's site
http://www.viaircorp.com/h-models/450h. If you look at their site the pump is rated at 1.04 c.f.m. @ 80 psi. From your photos it looks like you could mount a tank on the wall that the hose holder is mounted to. There are many sizes/shapes of tanks available and any size tank will help with airing of tires as even a 1 gal tank at 100 or 150 psi (depending on compressor) will expand a volume of double the size to roughly 1/2 the pressure very rapidly. I have "topped off" a tire with mine and the compressor didn't need to start. My suggestion wasn't a criticism by any means, It's just been my personal experience with having had several 12v compressors and several 110v compressors in my garage over the years that the larger the tank is the less the compressor has to work.