An example Library of textures to apply to the upper cabinet at the bottom of US&S Style B Semaphore TS2012's
The principle here is that if you want to use numbers in that same location, you will CLONE the semaphore, and CREATE YOUR OWN library like this one which contains the signal numbers for your route. Then edit the cloned semaphore's KUID table and change the KUID number that points to THIS asset to YOUR asset.
After that you can go into surveyor and select from your own list of textures, and when you are ready, upload both your semaphore clone and your library to the DLS for others to use with your route.