The last one is horrible and messy. I don't even know what you guys are talking about.
The only one that's somewhat pleasing to look at is the second because it was the only one where you managed to not make the colors suck so bad. otherwise, the lighting, flow, and composition are all off. Have you ever heard of the rule of thirds? I suggest you read up on it. It'll help with composition at least.
The third one has absolutely no depth whatsoever (and this is especially bad because that style of signature calls for it). Again, the composition is horrible. That signature is very uninteresting and oversharpened.
Spend more time on your signatures instead of finishing it quickly and posting