Same way as you do for the bricks.
- Open the set that contains the decoration in question in the Builder App
- Copy the latest files (i.e. those from this set) from the phone to your PC
- In the asset browser filter for textures, and look for items named like "1011231_0_VME_11085984_LEG_Top_1"
- Export them and you got a template
Those have usually not a great resolution, Torso prints are 512 x 512 pixels, 2 x 4 Tile 512 x 256 px
- Open the set that contains the decoration in question in the Builder App
- Copy the latest files (i.e. those from this set) from the phone to your PC
- In the asset browser filter for textures, and look for items named like "1011231_0_VME_11085984_LEG_Top_1"
- Export them and you got a template
Those have usually not a great resolution, Torso prints are 512 x 512 pixels, 2 x 4 Tile 512 x 256 px