smokeyb - 10:59 pm on Jan 26, 2005 (gmt 0)

We can, but it can be taken off easily

That is both true and untrue as it depends on the image. I'll concede that if your images are of black squares, and you have a white watermark on them, then it would be easy to repaint. But if your images are photographs or intricate designs, then although it can still be done, it is far from easy. It also presumes that people that are so unprofessional that they steal artwork, are actually graphic gurus after all, and would rather take more time being unscrupulous, than creative... Damn those Portugese ;)
However, it is besides the point in this instance, as the main purpose of a watermark is to be able to prove that it is yours, and it looks like that isn't an issue for you. But if you do watermark them in the future, the worst you can hope for is that lazy web designers will nick their images from someone other than you.
Smokey