Looking good sir, you're definitely coming along nicely! How long have you been using Photoshop?
I would take some of the criticisms lightly, eventually you'll find your own style and you'll only get better with practice. I got started when I was in high school. Find a couple of signatures or images that you really like and try to replicate them as best you can. You'll learn some new techniques that way and then apply that to your own work. Most people who make signatures on the two sites have their own look, they're pretty easy to spot. I say try and mix up the look of your signatures so you don't fall into that and they all end up looking the same. Almost every signature on the sister site that I see looks exactly the same, they're a lot more varied over here.