Not bad for someone doing signatures for a few months. Sig making is really fun.
Keep in mind that keeping the integrity of your signature's composition is important. You have flow going on which is great.
Utilize more effects like layer effects, adjustment layers, filters, apply image, fractals, C4Ds, etc. Define one source of lighting unless your render or subject calls for more.
Use more colors (not too much) that go with your render. If you think your sig is too colorful then tone it down a little. Don't make a monotone sig either.
Smudging can be your best friend. Experiment it with effects.
Your text should be more subtle. Don't make it 100% obvious. But don't get too fancy with it either. Use layer effects and colors that go along with your render but don't blend it in too much. It should still be visible.
The black space is good but try not to have too much empty spaces. You should at first attempt a signature with every pixel of space filled out.
A small border (1 px recommended.) may also spice up your sigs.
Make sure that whatever effects you put into your sigs is one with your render, or at least related.
Those are some general things from my 5 years of sig making (been doing it on and off.) Most of all, you should keep playing around with your tools and see what fits best in a sig. Your knowledge and flexibility will come from tutorials. Even the most basic tuts can have a major impact on a sig. Keep in mind that my suggestions are for rectangular sigs.
Hope I helped
