@Iluviaporos - Personally, I love re-purposing other items to use as outdoor flower containers, or using alternative materials. It can be tricky to get the look right so that it doesn't just seem like you've put a pile of junk outside and there just happens to be some plants growing in it, but I like to think we've managed to find the balance.
The trick seems to be to try and match up the colors of the different objects, so we basically just paint them all different shades of blue.
We've got an old wheelbarrow with herbs and some other objects like tea pots and tires and some of those big cinder bricks with the holes in them.
They make quite a cute, bright area of the garden and didn't cost anything except for time to put in place.