Those dimensions are more banner-like.
I like the colours and the way you put a drop shadow on it.

Anyway, some tips to make a great sig:

• Don't use fractals unless they look like C4Ds
• Only use one render, multiple renders makes it hard to create a focal and flow
• Add lighting that draws attention to the focal point
• Add text near the focal point, but not so that it distracts you from it.
• Don't use fancy fonts, basic fonts are always better to use
• Add depth by sharpening the focal and blurring the edges

And that's about it.

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