I am more just wanting to change the shirt types with existing assets, etc. Not actually doing complete new outfit, or still needs same thing?In game, through modding with Unity. In studio, find a scene card with a map you want.
You would have to alter the mod the same way it was made, with Unity to add the changes and a 3D modeling program to make the changes to the textures.
There are some on the Discord that come in scene cards for the studio like I have a forest one and a laboratory one, not sure about any available for in game.