I love google. After orkut, its time to give some nice look to your gmail box too. Recently google launched themes as gmail's setting option. You can read more about this the official gmail blog.
Official Gmail Blog: Spice up your inbox with colors and themes
In gmail settings, go to Themes tab where you can choose theme you like.
Mac4lin, have a look,
GIMP to achieve this. This will protect my images from inappropriate reuse. Also it will identify myself on web and if somebody needs original image, will contact me back, so I guess its a nice practice to watermark published images.