One of our friends had a 55 gallon drum that they had used as a planter, but as they were moving into an apartment, it got to be our 55 gallon drum. The drum is polyethylene and when we got it, it was cut in two top to bottom with some holes drilled in the bottom for drainage. It was also a nasty colour of blue.
So I decided to spruce it up a bit by painting it matte grey, adding some wooden legs and a wood trim at the top for some stiffness. Painting worked pretty well; the latex-based paint stuck very well to the polyethylene which surprised me. The legs were two 50 x 50 mm pieces of lumber screwed longitudinally along the base of the planter. The planter sits on the two legs which make for a nice, steady platform. After the planter was filled 3/4 full with potting soil, it looked quite nice.

Just add plants!
We planted jalapenos, tomatoes, fennel, lettuce, garlic, and beans. It is probably planted a bit too densely, but we will see how that works in a few months when harvest comes around.
A couple of weeks later, we had a bit of an incident with chickens in the planter and the beans were starting to get tall so we decided to add a trellis. It was made with some bamboo bolted to the planter and then lashed together in a modified A-frame. They seem to use a fabric rope made of t-shirt material here in NZ for gardening and it is quite nice and stretchy so I used that for the fabric part of the rope. Overall, I think the trellis added a lot to the look of the planter and I quite like it.

Bamboo spaceframe!