Crop Corner

Working in an empty new document, create the shape you want to use for your stamp. Add words with the Text tool; use the Brush and Pencil tools to sketch freehand shapes; copy and paste sections of other images into your design. If you're turning a photo into a stamp, try changing the photo to black and white using the Enhance>Adjust Color>Remove Color function. The apply the Filter>Artistic Cutout tool, adjusting the settings to achieve the level of detail you want. Finally, copy and paste the adjusted photo into the tile where you're creating your brush. Be sure not to save any changes to the original photo!