It also depends on what kind of signature you're looking for. While Johnny is right that a tag is different from what you're presenting, there's more than one way to tackle the problem. CSS can be a great way to implement a simple, concise design without the need for Photoshop (though, skill in CSS is important here too). It all depends on what you want! For me, I see the mock signature you made there easily built with coding, especially if you're going to have many changing pieces or a need to update it frequently (as one would with Nuzlocke challenges). That's something that can't be done as easily with a graphic piece.
Give what Johnny said a shot, learn some basics about graphic design if you want to go for the complete tag look. But don't forget about good old fashioned CSS either! Or hey, you can even use a combination of the two! Your options here are limitless. :)
