Sorry to say,but I didn't find the avatars that amazing,most of them are just selective color plays,and text in all of 'em look basic and IMO ruin the artwork.
I would suggest you to try out posterize,topaz,shapes[esp behind the text to make the text more visible[look at your palacio avatar,the first 'a' is not clearly visible].Next comes the text,in the palacio avatar,the 'rodrigo' text looks sublime,however the main text truly spoils the work, consider adding a white shape behind it.The text in the michu avatar looks disgusting[sorry if it is harsh] but yes,there are some good ones like the ferdinand and messi.
Looking at the signature,anyone can say you've improved leaps and bounds,really good that one,but it looks somewhat LQ,and again the TEXT,If I were you I'd put 'valentine' in some curly font say james fajarado or jane austen and 'stocker' in some bold font like bebas and then maybe darken the sides,also try this out add a gradient fill of black and white and set it to 'soft light'[this part is for finishing].
I've attached some textures below,consider using them:
PS: Mind passing the messi psd?,I can make something of it.