Ah of course, I'm glad you asked :)
When I started making siggys I was just editing the pictures, like adding color fx's and such, changing the picture into something more pretty. But later on it wasn't enough so I started making researches and downloading many textures and brushes. But in my opinion everything good comes from being creative and being original with the inspiration you have. So try practicing different things, and always follow art to keep yourself inspired from even the tiniest things. Deviantart and pixiv are great places to explore and find inspiration. :)
To start, simply find a background and some texture, next to harmonise colors choose a certain theme for the signature and continue adding different effects, testing out things is the best way of learning so. You will eventually find your own style and be more comfortable with the projects you make ^^.
I hope I can be helpful somehow;;