I double checked that im using the TBC version v3-bcc. For some reason i cannot change the border texture by picking a different type from SharedMedia Border in Borders>Border Texture. Every time i select a different one it defaults to Blizzard's tooltip border. All i can change is the color.

Border Edge Size doesnt work.
Changing the Background Texture doesnt work.

Doesn't seem broken to me. Looking at your screenshot, you're trying to use a texture from the "Garrison" directory which won't exist in BCC since the Garrison never existed then.

This are the options i got, none of them are working.

Also noticed that sometimes im able to change the border and sometimes im not, same goes for the background.