If you have Photoshop...
1. Open the stamp image file.
2. Give it a slight white area around the actual image so that you'll have margin when the image is tiled. This will make cutting easier.
3. Go to Edit > Define Pattern
4. Make a new document by pressing CTRL+N
5. Go to Edit > Fill
6. Click on Custom Pattern and you will see the stamp image you defined as a pattern in step #3.
7. Press OK