You can place watermarks on images in Step 5 --> Protect Tab. Gsphotopro has posted about a great free resource allowing you to design funky text watermarks>
gsphotopro:
For those who do not have Photoshop (you can get the Photoshop Elements program for less than $100 now) you can go to http://www.cooltext.com/ and generate text only based logos which are uh, er.. well, COOL (and free). These are saved as .gif which is currently supported on Shozam! and you can still use Shazam!'s "Way Too Cool Transparency Tool" to adjust you cool new text based watermark.
CoolText allows you to just type in your text and their online engine will render it for you as a custom graphic. you just download it to your computer and then point to that graphic file from Shozam! (Step 5 --> Protect tab). For best results make sure that you use as a PNG w/Transparency as a "File Format".
Here is an example of a tiny graphic, suited for one of the corners:
Here are some other images easily generated using some default settings provided by Cool Text. These would work better as larger watermarks, with a low Opaque value.
