Ideas to liven up booring square garden?

I have a front garden which is square lawn with a flower bed around it. At one edge is a wall, shared with the neighbour. In the middle there is a circular flower bed with a small ornamental tree in, surrounded by rocks. There are bushes at three of the corners, and at the other corner is a small stone pathway leading the way to the lawn. At the back near the house is a little bench on a gravel path. However, while pretty and colourful, it is boring and lacks height and interest as it's so symmetrical! Can anyone give me some ideas for how to liven it up and give it a bit of character please? I am not averse to changing the shape of the beds and things, and have unlimited access to rocks, bricks and wood, but absolutely no budget so any ideas have to be free! Thanks for any advice!!