That kenshin sig is so awesome!
I really love his younger/blood-thirtsy self more, just cause he's more badass
You deserve some cookies just for that
For the latest two, for the first, try some other fonts, stuff that isn't grungy, but is still relatively the same size
Also you might think about getting rid of some of that negative space and packing the effects in a bit more...
The second one, the render needs more blending. Try using some gradient maps or overlaying some solid effects over the render to achieve that. Also, I would suggest adding some C4ds to the piece to add more to it, and also get rid of some of that negative space. And the colors could match/blend better. And maybe think about putting the text on the side of the front wheel and curving it to fit the shape?