Whatever you like that fits, provided it has proper drainage holes. Pretty much anything that grows in the ground can be grown in a container, if it is sized accordingly. Mixed seasonal plants (annuals), various edible plants, mixed perennials and small shrubs, even a smallish tree or dwarf conifer. Or a mix of all. And of course, many houseplants

Do you intend to use it indoors or outside?

my concern was the depth, 12 inches doesn't seem deep at all to me and i'm not terribly familiar with root requirements of many plants (though googling helps sometimes)

gardengal, i intend to use it outdoors and planting season for us pretty much begins now.....

the container came with 3 one inch holes in the bottom.. i'm also wondering if that will be enough....

Should be fine and the depth is also OK for just about anything you want. Most roots grow out, not down but even so if you are growing a tree or shrub or something more or less permanent, you will need to unpot, root prune and repot with fresh potting mix from time to time. But that would be the case with any size container.

For perennials, annuals and most edibles, 12" is plenty of depth.

I garden almost exclusively in containers outdoors and they range in size from quite small (6"x6") to quite large (36"x48") but most are about the size of yours and I grow everything I described :-)

the depth should be fine. you should choose your soil mix carefully to make sure you don't have a high PWT since your container is more shallow.

you could grow just about anything in it. tropical and subtropical plants can be grown in Houston. a container will allow you to move it in the garage during a freeze (add wheels).

jrn 1/2 nursery and Caldwell nursery have a fair selection of tropicals. I use southwestern fertilizer for my other supplies (pbf, dynagrow fp)

If you like strawberries, it could be an option.