Adding Sample Background To Images

I noticed that in the contest area of this site, many designers protect their work by putting writing in the background. I can do this in Photoshop, but I was just wondering if there was a quick way that I could do this for a bunch of graphics.

Thanks in advance.

 

Try this: http://www.watermarktool.com/ (not my site.. but i've used it before)

 

Thanks for the fast response. That works.