Oval White Background?

I am looking to take this little picture and make the white background oval shaped around it. I would like to use this as a "stamp" to put on pictures that I take or different e-documents that I create. The problem is when I copy and paste it onto a picture it has a square white backdrop and it doesn't look as good as it would if it had and oval white backdrop.

Can anyone help me out? In advance of the warnings...I know that it has my name on it and that some TD freak will probably track me down and start stalking me but I don't give a crap, just looking for some help.

TIA

Image that i would like altered

Example of the square background that I would like to be oval.