The colors really aren't working for me. Sorry. I think there should be a light source and more depth too. The effects seem incredibly random, especially the splatter brush on the left. **scratches head** Read some tutorials.
The concept is nice. If you use the pen tool, I would always use a soft brush on such signatures or do a clipping mask when using a hard one. That was the first thing. The colors are chosen too randomly, they do not fit really to each other. To make them fit better, just use some gradient maps or so, they will work well, put em on soft light or so at a lower opacity. The background is a bit too sharp as well, blur that one a bit and add few C4D effects over the guitar so the flow is even better. Finally your source of lighting is missing, either you use a 200 px soft brush in the white color or you can use many C4Ds put NOT randomly at a specific spot, the downer end of the guitar you have there would work well. I hope I could help you. Tutorials are nice, too, but I think experementing is more fun.
