I typically find inspiration and experimentation with different styles to be very helpful.
My story is that I constantly delve into slumps and lack of creativity. This is because I find a new style, work with it, then eventually turn to smudging. This happens all the time for me.
I would suggest not to work with a style with which you're familiar (not that you shouldn't at all; I mean you should find a diversity of styles and simply incorporate in your sigs these new styles along with your "signature" style). In any case, I personally believe there is a multitude of inspirational pieces in
here.
As for tutorials, well, I don't know if those will necessarily help you. I believe they are good for seeing how a person makes a sig and are useful for beginning artists to learn some techniques in making sigs, however I don't think following tutorials will necessarily help you out of slumps and/or inspire creativity. Well, they may inspire creativity by providing new techniques about which you never thought, but eh... I'd look through the thread and work from there.
Avatar: In memory of ieatwyverns <3
Thank you, Vasco <3