well all i see is a stock and you have put everything on it and not under it, and for the text it's so big, here are some tips for you:
* Try to add the effects behind the render and if you want to put after render then try out some tutorials there are a lot of in this world.
* Well you see in your signature you hardly can put something so try this size, 400x150 Px.
* See any signature the text's are kinda small, i mean they put their name about 16 Px or even more smaller and then the second text they make more smaller or sometime they write like you did " gfx designer " big and the under that a small font which is the main text.
* Add some flow because putting flow make your signature to understand you see there is gfx own language " like you need to explain the flow, and put some depth and lighting - but in ur case dept is bad and lighting is good but not perfect.
* Add borders, i saw all gfx'rs that do signature they sure put a small border, a example when you write something or even draw something in a normal page to make it more beautiful you stroke the drawing, so this is a same case.
* Learn smudging - smudging always put to the signature a flow , and smudging help us to see the render clearly.
well follow those tips and you can be more better.
Regards,
~Ace~