I'm liking the last three, even if they are unfinished. The Hei one is my favourite by far, but I like the effect the third one has (I'm guessing that's One Piece? I haven't ever watched it). I think you could do more with the Optimus Prime sig. Making his eyes glow bigger with a sort-of darker background seems like it might be pretty cool.
For some reason though, I'm not a fan of the first. I like the text style/position. And the render is cute. But I'm just not feeling it. I can't really place my finger on it.
As for the avatar for DS... I would change the font to whatever font you used for FFVII in the sig. Make it black, maybe lower the opacity slightly so it doesn't stick out too much. I just think the current font looks tacky at the "VII" part.
Anyways... here's my attempt at finishing the Ikaros sig.
I removed all smudging from on top of the render, but I left it smaller and moved to the right like Bill suggested earlier. If, now without the smudging, it feels like there is too much empty space, I can put the larger render back in and adjust accordingly. I tried something simple with text, so hopefully that serves it purpose. So anyways, comments on this one now.
Also, here is another sig that I had actually been working on before my current set, but just threw the finishing touches on it.
Definitely not one of my best, but I kind of like it. The text might be too overpowering though.