I don't see anything wrong with your attached files. I went ahead and Google'd sm_stickers and saw that it's using RegConsoleCmd. You will need to change your plugin commands located within in the source code to use RegAdminCmd if you want your overrides to work.
Code:
void LoadCommands()
{
RegConsoleCmd("sm_sticker", Command_Stickers);
RegConsoleCmd("sm_stickers", Command_Stickers);
RegConsoleCmd("sm_st", Command_Stickers);
}
->
Code:
void LoadCommands()
{
RegAdminCmd("sm_sticker", Command_Stickers, ADMFLAG_GENERIC, "Toggle stickers");
RegAdminCmd("sm_stickers", Command_Stickers, ADMFLAG_GENERIC, "Toggle stickers");
RegAdminCmd("sm_st", Command_Stickers, ADMFLAG_GENERIC, "Toggle stickers");
}