I've always meant to try and design a semi-unique watermark that I could use appropriately on a photos I upload to Flickr. After fuddling around with some ideas, I came up with a solid design I'm pretty happy with. My goal isn't to put the watermark on every photo, but try and include it when it looks right.
Nothing too crazy, just a sketch of a 35mm film camera and the font "Die Die Die" which gives the look of text being scribbled on something.
Thus far, I've gone through and added the watermark to a few of my photos with borders. For the most part, I think they really give a sense of balance to the overall composition. Before, the black borders were too empty and distracting. Obviously, I liked the look, but I always felt like it was missing something. I think a watermark was just that thing.
Here are a few of my past photos that I re-edited to include my new watermark.