Here is whats happening in your sigs.

1st.
-Needs better blending.
-No TEXT?
-Do not use too much C4d's on top of the image.
-Need to work on Focal Pint.
-Need to work on Depth.
-Foot of render was trimmed.
-Bad Aligned render.

Final Rank: Novice

2nd.
-Again, too many C4D's on top of render.
-No TEXT?
-Somewhat has a focal but needs more work.
-Needs more depth.
-Low quality render used.
- Too much color on render.

Final Rank: Novice

3rd.
-C4D's Don't follow a pattern.
-Need to work blending the render.
-Color scheme seems different from left to the right side.
-The blue orbs do not match with the render.
-Low quality render used.
-Wrong lighting.

Final Rank: Novice

4th.
-Need to work on depth.
-C4D's placed incorrectly, need to erase parts to see the group.
-Great TEXT positioning.
-Great Color scheme.

Final Rank: High Novice.

5th
-Need to work with depth.
-Need a focal point.
-Low quality background.
-Need to work more on merging the render and background.
-Low quality render.
-Wrong light positioning.(example- If the flash of light is in the right then only the right needs to be shining.

Final Rank: Novice

5th
-Low Quality render.
-Need to work in depth.
-Need to work on focal point.
-Good Text placement but very weak color.
-C4d somewhat matches the flow but need to work more on that.

Final Rank: Novice.

6th.
-Work on depth.
-weak background.
-Focal? yes and no.
-need to blend with background.
-need to work on background.

Final Rank: Beginner.

OVERALL SCORE:2 (NOVICE)

Since all of the sigs have been made and done the same way or alike in technique here is what I have to say for all in general.

-No flow
-No Focal
-Need to work on text.
-need to work on blending renders and background.
-On some you need better quality renders.
-Text positioning.

OVERALL SORE:1 (Beginner)