Minna is right,but that doesnt mean that you are not good at making sigs...You are just new to the forum ,and you need kinda time to used to the forum and also making awesome signatures like Minna's for example(personal i love Minna's<3<3<3~~~)...Just keep tryingYou need to put more effort into your sigs, try using cinema 4ds (I don't use them much tough), new brushes, patterns. Find a few tutorials for stuff like blending in renders, smudging....If you do I'm sure you'll get better. And try using sizes like 360x140 or 400x180...around that...because in my opinion your signatures are too big. Look at the size of my sig.
btw...welcome to NB.