You also have no way to rotate it, increasing the chance that they will be no good when you need them. Regarding plastic buckets, these are harder to store discreetly, due mainly to their size. One suggestion I've heard involves hanging a full-length curtain, or putting an Oriental folding screen a foot or so away from an existing wall. You can stash loads of buckets back there, but the obvious drawback is a loss of space. It is not a lot of living space, but if you're already in a small living area, this may not be possible.
Buckets are better suited for closet floors, since buckets are bulkier and closets offer more space.
You also need to consider their weight. You don't want to store heavy 6-gallon buckets on high closet shelves, because in the event of an earthquake, you definitely don't want it all to come crashing down to the floor. If you're really low on ideas, you might even consider making furniture from your buckets. We have a customer who stacked two of our superpails together, secured a round piece of wood to the top superpail's lid, and threw a tablecloth over the whole thing. Just like that, you've got a sturdy nightstand, for next to nothing.