Ok, first of all, the afro one. That c4d on the right need to be blended in more(use Ctrl + U and mess about with the colours).
With the render, try smudging around the edges of it so it blends in a little bit more.
Near the top of his afro there's some blue text, get rid of that, it doesn't look right.
With the text and the boxes, move them closer to the render. Try clipping masking the text and seeing what it comes out like, then maybe a 1px black stroke?
Ok, now for the coke one...i quite like the concept of it. In the smudging there's a kind of grainy bit, try and fix that as it doesn't look too good. Maybe chop off some of the left side so it's not as plain.
But, good work Legend. Glad to see your getting back into GFX!