Ok,i see you center you render/stocks quite often =P it's ok but for me i usually never center my focals because it is less appealing to me. Also when lowering the render size , try to keep it how it was , like not so strectched .Or it would cuase bad quality.
-Work on your text , i really like the text on 4th to last .Some have err text that don't quite blend.

Best tag you have is probably 3rd to last. I love colors . Quality is nice how it is.