Sadly, no. If you choose to use the (adorable!) image Nence made, you wouldn't not be able to keep your furrever friends stamp. The Arena has a limit on signature image sizes. While you can have more than one image, the combined images cannot take up more than a 500p x 200p space, and the two together would be too long.
If you can resize the image Nence made to a smaller size you can put them together. Reszing can be done with photoshop or similar photo editors. Signatures can be added to your profile with [img] [ /img] links. If you have any trouble you can ask for help in the sigs & site support forum.