Can one of the smiley images be added to a signature?

I see where some people have images with their signatures. Can a smiley image be used in the signature area and if so how do you add it? Thank you.

 

This is the one that I like Frank.

 

That is a cute one Tammy. A reminder of what we all look like through out the day!

 

Looks cute.

 

That is so cute! Thank you. The only thing missing is a wrist brace like I have to wear from using the computer so much!

 

Awww! Cute.
Frank takes such good care of us stewbies, doesn't he?

 

Yes, daisybeans he is very good to us indeed. I just love that little smiley typist. Doesn't take much to make me happy!