>>46574580I got ice or fighting and a free pick. I think I'll go Ice/Steel
Theme could be a mountain with hikers and other trainers working their way up. Most of them train Ice or Steel types to help them with the ice and snow (it would always be hailing in the gym.) Gym puzzle would be the player climbing up with help from an Alolan Sandslash, which would dig wherever told to find caves that go higher. At the top you meet the gym leader, who reveals you've been helped by his ace, who was studying your team.
His team will be:
Aggron
Crabominable
A. Sandslash
Aggron may be a little overkill, but 2/3 members are 4x weak to fighting, making him easy to beat if you're prepared.
Badge can be the peak badge, I made a rough drawing, it shows the snowy mountain the player has now conquered.