I think your main problem here is your colours.
Like you chose a venom render which is black and white and made a blue, white and black bg. Just try to get your basics going here. Read up on tutorials on flow, depth and composition.

Anyway I'll give a little cnc on each

1st)
As said the colours don't match too well. I'd be going for your black/white/grey colours here with some small amount of red.
The trouble with these popout sigs is that it's hard to create decent composition and depth. Also it looks pretty bad when parts are cut off like here.
TBH I'd also get rid of the text and that black rectangle as well.

2nd)
This is probably my favourite here. The colours go pretty well together.
Here you have overblurred the bg and it looks rather lq. Try not to overdo blur. TBH tags with just brushwork don't need blur at all.
Scrap the arrows and the text as well.

3rd)
You blurred the render for some reason here o.O
Don't do that. It looks lq. Renders are meant to be your focus so they're meant to be a bit sharper than the bg. The text isn't very good either. I hate text so that's why I only add it for gifts. If it wasn't for the blur this will probably be my favourite of the lot. It has the best composition out of the lot and blends a lot nicer.


As said just keep looking up tuts and making signatures.
This forum is for progression in GFX so don't be discouraged.
KIU mate