Hi! If you've "played" through the template project before and used the same names as the ones there (as in, the cg_2 for example) and only changed the image paths, the issue might be that you've "unlocked" it that time so it stays unlocked. You can try the "delete persistent" button in the Ren'py launcher. Be careful that it deletes all persistent data (so, persistent variables).
If they don't show up in the gallery, check that you first defined the buttons (in the init python block) then created them (in the gallery pages themselves, you can see the 'add g.make_button' lines there.)