Regarding your style, my friend, I would say that your use of mostly fantasy subjects, choice of NMM, and use of saturated colors would place you squarely as a high chroma, high contrast painter similar in style and approach to Glazed One or Glazed Over...whatever his name is.
I will say that one thing some of my favorite 2d oil painters say about beginners is that we always go too bright and saturated with our colors. I have been advised to always take a gray-er version of the color I initially intended to use. This doesn't always mean gray, but desaturated in some way. I've actually recently just added the compliment of any given color to dull it down. While your fantasy style suits you and is perfectly lovely, you mentioned wanting to challenge yourself. I reccomend painting a figure with a very dull pallet. Artists of a variety of media do this, even in fantasy, such as Bonner, Frank Frazetta, etc...
Another way to push it to the next level for you...I reccommended this to BaM because of his painting speed, but the way you are knocking them out you could also pull it off: Make a huge battle scene or diorama with multiple models. Think of Jarhead's epic tiranid/SM scene, but not painted en mass like he did and not quite of that proportion. If you really want to leave your mark on the mini painting community, you need a dio of epic proportions. You have the skill, speed, and dedication to pull it off.