Ok so I'm only going to comment on two works because I'd be repeating myself a fair bit, but hopefully you can take something from this. If I seem harsh, I'm not trying to be, I'm just trying to help, so yeah.
http://fc09.deviantart.net/fs70/f/2011/144/a/3/naruto_tag_by_xyr1n-d3h5ate.jpg
So firstly, I'd like to point out that this probably isn't the best way to use C4Ds. Firstly, because it is on such a low opacity, it isn't really adding any flow or impact within the tag, and because it is directly and isolated to being over the focal, it just makes the render look lower quality. As a general rule, try not to cover the focal point (face), and if you are going to put effects over the render, just cover corners and little sections on the outsides of the render so that it helps blend it in, but doesn't take focus or hide parts of the focal.
Also, the tag is way too simple. It is ok to have a gradient/solid colour as the background, but you really need to fill up some of the background with effects so it doesn't just look like a render on a colour background with some text to the side. As for the background, you've got the right idea of having the lightest point at the focal and getting darker as you move towards the edges, however with that yellow colour, it doesn't look too great as that mustardy colour at the edges. You could've tried a grey / black from his clothes, or perhaps a dark blue which would've made it look a little less monotonous.
Finally, it's good to see you've blurred and sharpened the render a little bit to add depth, however you possibly have gone a little extreme in both directions, parts of the face look a little low quality from too much sharpening, and the body is way too blurry.
http://fc07.deviantart.net/fs70/f/2011/096/2/f/tags_by_xyr1n-d3dcmlr.jpg
You said this was one of your earlier ones, and yet this one is by far your best (tutorials can be of great help until you reach a certain point where you can't really learn from them any more). I'd recommend continuing using tutorials for a bit longer until you grasp the key techniques a bit better.
But on to the tag, the only real thing I'd advise against in this tag is the text and the duplicated focal. The text is too far away from the render and is just drawing focus away from your render, and the duplication is doing the same / doesn't really look that good. Something else I'd tidy up are the white pixels around parts of the render like the hair / back, and on such a dark tag, they are quite obvious...
So, the good parts of this tag are the fact that you've got lots going on and more elements. You have the C4D used way more effectively than the last tag because it is more solid and asserts itself, and the splatters fill up the background a bit so it doesn't look so plain. Also, you have splatters over parts of the render, but away from the face (focal point) which blends it all together without detracting.
Honestly, this tag is much better than all the rest. Either try and do some more like this one, follow some tutorials, or just look to put more in your tags.
Hope that was helpful / not too harsh!
