Loki: The text looks weird in both places o.o And for some reason, it keeps reminding me of that Death Note movie, L: Change the World. lawls. Anyway, it's an interesting banner. But I sort of have mixed feelings about it x___o I don't tend to like it when vectors (with the circles in the background) and effect C4D's are put together. However, you sort of managed to pull it off. What I don't like is that some areas of C4D look a bit messy, especially around the face. I like the colours xP And the flow is alright, even though it sort of goes \ instead of following the render.
Gummy: I can't say I like the blurriness o.o Nor the outer glow around the text, since it looks like the text is hogging up all the attention. It's an interesting mix of vector-ish brushing. They all look okay, especially the scribble sort of brushes in the background, but I don't like how the flowery sort of brushing is in front of the render. Also, I think it needs moar colours~ Ah, and the scanlines seem to fit in.
YunaDances: I agree with CheesePeow on this one. The render totally doesn't match the background xD Especially since the render is all soft, and sort of blurred, whereas the spatters in the background are 'stronger' I guess. And the grid thing in the background looks pretty weird as well. Though I like the fact that there's all those colours in it xD
CheesePeow: ... I like it o.o The colours are a tad bit bright, but in comparison to the old one, it looks a lot better. I like the soft blues, with the white, and the pale yellow~ The text does look a bit distracting, though. And I see slight hints at depth, but it looks mostly flat. I don't really think that the scanlines are needed, but like I would know xP And I was going to say something about lighting, but your banner seemed bright enough to not need lighting.
Perfectionist: That's... pretty good, especially for a first try o.o The colours of the background don't completely match the render, but it looks pretty great. It needs some sharpening, and maybe a little bit of render blending, or perhaps some gradient maps, but otherwise, it looks nice.
Motsuko Live: Hooray for C4D backgrounds xD The effects are pretty cool, but in my opinion, the render needs to be blended into the background even more, because it sort of just sticks out. Gradient maps, or colour blending layers like that should work, I think. And the border seems a bit unnecessary. Or I've just (re)started to like border-less banners o.o
If you didn't notice, my comments got crappier towards the end. Sorry about that. I sort of ran out of things to say >.>