Here are a couple more examples of what you can do with a picture of pretty much anything... even grass.
You just have to play around with it to see what you can come up with. Here is a screenshot of the editor in Picasa, the red arrows are some of my favorite tweaking tools. "Invert colors", and "Duo-Tone" are good ones.
and "neon" too.
So then after you make your image, take it to a print/copy shop to have it enlarged (make sure your original image is high resolution before altering in Picasa if you are going to enlarge it.) If there is no print/copy shops close by, you can have your photos enlarged online. I've used PosterBrain, and have had good results. Look at all the fun you can have with it.