In my opinion, 'style' just happens; you will discover it when you look back at your work over a period of time. You'll suddenly notice that you like certain colors a lot, or that you really prefer the work you do in one medium over another or one subject matter over another. I used to fret constantly about this style issue, liking everyone else's and not seeing that I had a valid style as well! In fact, in many ways it was one of the biggest wastes of time, worrying about needing a style.
My best advice is to try everything (medium, materials, technique, color palette) that appeals to you, like clothing. The items that suit you will stay in your closet, you'll discard the ones that don't, and sooner or later you'll end up with a particular wardrobe that is uniquely your own. It'll happen when it happens, and those who toss their own natural inclinations to doggedly follow every trend or become the flavor of the moment often melt away quickly because they haven't found the enduring appeal of their own art for themselves.
You need to be able to like to produce your own art even when it's not trendy, however, there's a lot to be said about being able to adapt a look that's in vogue when it comes to commercial work, so flexibility and the experience of experimentation will serve you well in that way. Eventually, you can say no to work that doesn't appeal to you for a variety of reasons, and what you are left with will typically be the work you love to do, in your true style.
And in any art museum, portraits are everywhere: in every style, color, and size, from every country and created by every type of artist.
In a portrait's brushstrokes we find a path connecting us to another human on a timeless level.
Da Vinci's Mona Lisa, van Gogh and Rembrandt's many self-portraits, these are just a few of the well-known portraits that have come down to us through the ages. Their popularity is testimony to the power and value of capturing personality, character, and aspect, on canvas.
Oil paint captures the living qualities of the human face and body like no other medium. Skillfully handled, the portrait transcends technique and draws the viewer in, and a single artist creates a treasure for us all.