I can tell that your skills are quickly progressing, just by comparing the top signature with the bottom three. You are definitely getting better at rendering backgrounds with smudging, blending, sharpening, etc. However, I think you need to work on how you blend the main figure/focal point with the background; the robotic woman appears to be thrown on top of the signature instead of being part of the background, especially the large hand on the right side of the signature. It looks like the outside of it has quickly been smudged.
Another thing you should work on is creating dramatic lighting, which adds depth to the piece. Intense lighting can be achieved through using a soft brush (or any other brush that looks cool) in certain areas on a separate layer and changing that layer's blending mode. This makes darker areas (background) become darker, and lighter areas (main figure) appear lighter.
Also, consider making your signatures much smaller, maybe half the size of your current ones. There are some issues with your typography as well (Trajan Pro is extremely overused), but worry about that later on once you've gotten better with the actual graphic elements of the signature. Finally, like others have said, tutorials are very helpful! :nuts:
GL
