It seems to me from looking at your skins that you need to work on the dark and light areas of the skin as it's just one basic colour mostly, you need to define those areas to stand out from each other instead of blending into one, so you need to select colours slighty lighter or darker than the base colour you are using

I do most of my designing on skinedit especially the shading and sometimes use paint.net for added effects, with skinedit i basically use HSV and increase or decrease in value to create the shading :P