Adding a watermark on your photos can help protect people from taking them.
When you choose watermark photos, the watermark is applied to the photos when they are uploaded with the exception of the original uploaded file.
There are several options in the placement of the watermark. In those options is a "tile" option. This will tile the watermark file over the entire photo.
There is also an option to add a logo to the photo. This will also need to be a .png file and you don't want this one too large (around 150 x 50 pixels).
Creating your own watermark
Watermarks are transparent png files that are applied over the photo. You will need to use Photoshop or some photo editing program to create your own watermark.
Start with a photo that is around 1600 pixels wide at 72 DPI. Add the text over the photo you want to be the watermark. White text is best.
Add a drop shadow to the photo. These are suggested settings for the drop shadow.
Blend mode: normalOpacity: 100%
Distance: 3Spread: 100%Size: 0-3
After you get the text how you want it, set the opacity of the text layer somewhere between 10 - 40%.
Hide your background layer so you only have your text layer(s) showing.
If you are going to set the watermark to apply in the center or one location of the photo, trim your file to remove all the excess transparent space. Image > Trim > Based On: Transparent Pixels , trim away all > OK.
If you are going to set the watermark to tile over the photo, crop the watermark so there is spacing on all sides.
Save your watermark file. File > Save As then in the Format option in the dialog window, select PNG (.png). PNG options: Interlace: None.