One of these?
Here is the code for each one, you can either copy/paste or type it in manually (I've not used either a Kindle or iPad, so not sure the limitations). I added a couple spaces so that the text displays here instead of the images, just remove the spaces when you enter it into your signature:
[img ]http ://i50.tinypic.com/27y0mt0.jpg[/img]
[img ]http ://i50.tinypic.com/28i3f5k.jpg[/img]