I think I never mentioned that, but back when I had free time, I used to work on a Pokemon region based on Scandinavia
Here is my most thought through Pokemon OC with his team, featuring some regional forms and a new mon
Enjoy^^

On the left we have the regional form of Tyranitar (Ghost/Rock) and Ursaring (Ice/Fighting). And below is a fully new fairy/fighting bull that evolves from the regional form of Tauros.
I partly made him up as a gym leader of a new region although with only three of his pokemon since he'd team up with his boyfriend in the fight. I thought of it as a little less of the traditional gym and designed it more like a small national park where you have to get to the top of a mountain, but before you can actually compete in the gym challenge, you gotta do him and his bf a little favor and talk to (and battle) bf's father, who is against him running the gym together with my oc.
Once you fought and convinced him to watch the match, you can enter the national park/gym.
It has wild pokemon and trainers, not set to a specific type but more of a theme, that being the area you are in as you climb the mountain. So a lot of ground and rock types with gras at the start and ice at the top.
At the top the couple awaits you in the arena formed by some standing stones (like a stonehenge with more space for battling in the middle), and the double battle starts. Since I imagine this to be probably the final gym of the region, you'd face a full team of six, each of them having three. For my oc I think it would be Tyranitar, Mamoswine and Lycanroc. For his bf it would be steel as a type. His family claims to be an old 'noble' family so Bisharp, Aegislash, Corviknight are common for them, but he also got an Aggron, Lucario and maybe Steelix from his OC bf. In the double fight he might use Bisharp, Corviknight, to please his father who is watching, as well as maybe Lucario to show that his bf is helping him.
Upon Victory, the player would gain the Summit Badge.
Later you can recruit one of them to be part of the Elite Four (which you will recruit entirely fresh in the mainstory), while the other manages the gym or maybe you can recruit them both and someone new takes over the gym, idk yet. Would be kinda funny to see the father take the gym over now, that the fight he watched rekindled his love for battling again as well or something haha
At least that are the basic ideas.

Its just a little mind game for fun, but I would love to hear what you think^^